Abstract:
An air filter has a housing, a filter core, a resilient abutting element, a sleeve, a threaded rod bracket, a threaded rod and a nut. The axial sealing is achieved by axially compressing the resilient abutting element, such that the user does not have to apply much physical effort to compress the resilient abutting element. The user can easily push the filter core into the housing, and then rotates and tightens the nut, which can axially compress the resilient abutting element. It is easy to apply force on rotating the nut, and better still, the nut can be rotated by an electric tool, which further facilitates the convenience in assembling. Besides, the nut only abuts the sleeve, and the threaded rod bracket does not abut the filter core. Consequently, the filter core is not blocked, thereby making the air smoothly pass through the filter core.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims priority under 35 U.S.C. 119 from Taiwan Patent Application No. 103126106 filed on Jul. 30, 2014, which is hereby specifically incorporated herein by this reference thereto. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an air filter, especially to an air filter for filtering suspended particles from air. 
     2. Description of the Prior Arts 
     An air filter is a device for filtering suspended particles from air, and is usually installed in a ventilation system of a building, an air compressor, or an engine of a vehicle. The conventional air filter such as an air cleaner disclosed in U.S. Pat. No. 6,190,432 as shown in  FIG. 8  comprises a housing  91 , a filter core  92  and a sealing system  93 . The housing  91  has a first housing  911  and a second housing  912 . The first and second housings  911 ,  912  are assembled together, and an accommodating space is formed between the first and second housings  911 ,  912 . The first housing  911  has an outlet  914  communicating with the accommodating space. The second housing  912  has an inlet  913  communicating with the accommodating space. 
     With reference to  FIGS. 8 to 10 , the filter core  92  is mounted in the accommodating space and has a wavy filtering sheet  922  and a flat filtering sheet  921 , both for filtering suspended pollutants. The wavy filtering sheet  922  and the flat filtering sheet  921  are rolled into a cylinder and are alternately stacked to form multiple layers of the wavy filtering sheet  922  and layers of the flat filtering sheet  921 . Thus, two surfaces of each layer of the wavy filtering sheet  922  are respectively flush with two adjacent layers of the flat filtering sheet  921 . Multiple channels  923 A,  923 B are formed between each layer of the wavy filtering sheet  922  and the two adjacent layers of the flat filtering sheet  921 A,  921 B. An end sealing adhesive layer  924 A is adhered between each layer of the wavy filtering sheet  922  at the side adjacent to the inlet  913  and one of the layers of the flat filtering sheet  921 A that are adjacent to said layer of wavy filtering sheet  922 . Thus, the channels  923 A between said layer of the wavy filtering sheet  922  and said layer of the flat filtering sheet  921 A are sealed at the side adjacent to the inlet  913 . Another end sealing adhesive layer  924 B is adhered between said layer of the wavy filtering sheet  922  at the side adjacent to the outlet  914  and the other layer of the flat filtering sheet  921 B that is adjacent to said layer of the wavy filtering sheet  922 . Thus, the channels  923 B between said layer of the wavy filtering sheet  922  and said layer of the flat filtering sheet  921 B are sealed at the side adjacent to the outlet  914 . As a result, the air to be filtered enters the cylinder-rolled filter core  92  from the inlet  913  of the second housing  912 , and then enters channels  923 B, which are not sealed at the side adjacent to the inlet  913 . Afterwards, the air axially moves to the other end of the channels  923 B, and is unable to flow out from the filter core  92  due to the end sealing adhesive layer  924 B. Thus, the air would pass through the layer of the wavy filtering sheet  922  to arrive at another channels  923 A, such that the air can flow out from the filter core  92  to arrive at the outlet  914 . When the air passes through the layer of the wavy filtering sheet  922 , the wavy filtering sheet  922  filters the suspended particles from the air to clean the air. In addition, the air may pass through the layer of the flat filtering sheet  921 B to arrive at another channel, and said layer of the flat filtering sheet  921 B also can filter the suspended particles from the air. 
     With reference to  FIG. 8 , the sealing system  93  has an annular frame  931  and a seal member  932 . The annular frame  931  is mounted around the filter core  92  in an end adjacent to the outlet  914 . The seal member  932  is mounted around the annular frame  931  in an end adjacent to the outlet  914 , and transversely abuts an inner wall of the first housing  911 . The seal member  932  is made of pressable and resilient material, and an original outer diameter of the seal member  932  is bigger than an inner diameter of the first housing  911  at a position corresponding to the seal member  932 . The seal member  932  is pressed transversely to transversely and tightly abut the inner wall of the first housing  911 , thereby transversely sealing a gap between the filter core  92  and the first housing  911 . Accordingly, the air to be filtered must pass through the filter core  92  to arrive at the outlet  914 . 
     However, the conventional air filter has the following shortcomings. 
     First, the sealing system  93  seals the gap between the filter core  92  and the first housing  911  by transversely compressing the seal member  923 , and thus the outer diameter of the seal member  923  is bigger than the inner diameter of the corresponding position of the first housing  911  as mentioned above. Accordingly, installing the sealing system  93  into the first housing  911  is difficult, since the user has to apply much physical force to push the sealing system  93  into the first housing  911 . 
     Second, with reference to  FIGS. 9 and 10 , the conventional wavy filtering sheet  922  and the flat filtering sheet  921  are adhered to each other by adhesives  925 . The adhesives  925  are spread on a surface of the flat filtering sheet  921  and extended along an elongated side of the flat filtering sheet  921 . Since the wavy filtering sheet  922  undulates as a wave, the flat filtering sheet  921  only adheres to a small part of peaks of the wavy filtering sheet  922 , and thus the adhered area between the flat filtering sheet  921  and the wavy filtering sheet  922  are too small to securely connect the filtering sheets  921 ,  922  to each other. Besides, the adhesives  925  are spread between any two peaks, and thus occupy a part of the space of the channels  923 A,  923 B, thereby interfering with the flowing of the air. In addition, since the adhesives  925  are spread on only one surface of the flat filtering sheet  921 , each layer of the wavy filtering sheet  922  is only adhered to one of the layers of the flat filtering sheet  921 B, and is not adhered to the other layer of the flat filtering sheet  921 B. As a result, the connection between the flat filtering sheet  921  and the wavy filtering sheet  922  is not strong enough. After in use for a period of time, the wavy filtering sheet  922  and the flat filtering sheet  921  may have stained with suspended particles, which lower the filtering efficiency. Therefore, to clean the wavy filtering sheet  922  and the flat filtering sheet  921 , clean air is blown into the filtering core from the outlet  914 . When the clean air passes through the wavy filtering sheet  922  and the flat filtering sheet  921  in a reverse direction, the air brings the stained suspended particles out of the filtering sheets  921 ,  922 , and the air is blown out of the inlet  913  together with the suspended particles. However, the connection between the flat filtering sheet  921  and the wavy filtering sheet  922  is not strong enough, and there is no annular frame  931  in an end adjacent to the inlet  913  to axially abut the filter core  92 . Consequently, as the air blows, the layers of the wavy filtering sheet  922  and the flat filtering sheet  921  in the center of the filter core  92  may separate from each other and axially protrude out along the blowing direction of the air, which causes the filter core  92  to be dysfunctional. 
     Third, with reference to  FIG. 8 , as mentioned above, the annular frame  931  axially abuts and fixes the filter core  92 . The annular frame  931  has multiple connecting ribs  9311 . The connecting ribs  9311  are transversely connected to an inner wall of the annular frames  931 , and axially abut the filter core  92 . However, the connecting ribs  9311  also block the channels of the filter core  92  at the abutment position of the connecting ribs  9311 , and thus the air flow is interfered. 
     To overcome the shortcomings, the present invention provides an air filter to mitigate or obviate the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     The main objective of the present invention is to provide an air filter that has an easily-installed filter core. 
     The air filter has a housing, a filter core, a resilient abutting element, a sleeve, a threaded rod bracket, a threaded rod, and a nut. The housing has an accommodating space, an inlet, an outlet, and a first stepped surface. The inlet and the outlet communicate with the accommodating space. The first stepped surface is formed annularly around an inner wall of the housing. The filter core is mounted in the accommodating space of the housing, and has a through hole. The through hole is formed axially through a center of the filter core. An outer diameter of the filter core is bigger than an inner diameter of an inner periphery of the first stepped surface of the housing. The resilient abutting element is annularly formed on a periphery of an end surface of the filter core that is adjacent to the outlet, transversely and axially wraps said periphery, and axially abuts the first stepped surface of the housing. The sleeve is mounted in the through hole of the filter core, and is adhered to a hole wall of the through hole. The threaded rod bracket is mounted securely in the accommodating space of the housing, and is disposed between the filter core and the outlet. The threaded rod is mounted securely on the threaded rod bracket, and is axially mounted through the sleeve. The nut is mounted around and is screwed on the threaded rod, axially abuts the sleeve in a direction toward the outlet, such that the resilient abutting element axially and tightly abuts the first stepped surface of the housing via the sleeve and the filter core to axially seal a gap between the first stepped surface and the filter core. 
     The axial sealing is achieved by axially compressing the resilient abutting element, such that the user does not have to apply much physical effort to compress the resilient abutting element. The user can easily push the filter core into the housing, and then rotates and tightens the nut, which can axially and indirectly compress the resilient abutting element. It is easy to apply force on rotating the nut, and better still, the nut can be rotated by an electric tool, which further facilitates the convenience in assembling the filter core into the housing. In addition, the nut only abuts the sleeve, and the threaded rod bracket does not abut the filter core. Therefore, two axial end surfaces of the filter core are almost completely unblocked, thereby ensuring the air can smoothly pass through the filter core. 
     Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an air filter in accordance with the present invention; 
         FIG. 2  is an exploded perspective view of the air filter in  FIG. 1 ; 
         FIG. 3  is a side view in partial section of the air filter in  FIG. 1 ; 
         FIG. 4  is an enlarged side view in partial section of a resilient abutting element of the air filter in  FIG. 1 ; 
         FIG. 5  is an enlarged side view in partial section of a nut of the air filter in  FIG. 1 ; 
         FIG. 6  is a partial operational perspective view of a filter core of the air filter in  FIG. 1 , showing the filter core expanded; 
         FIG. 7  is an operational side view in partial section of the filter core of the air filter in  FIG. 1 , showing the filter core expanded; 
         FIG. 8  is a side view in partial section of a conventional air filter in accordance with the prior art; 
         FIG. 9  is a perspective view of a filter core of the air filter in  FIG. 8 ; and 
         FIG. 10  is a partial operational perspective view of the filter core of the air filter in  FIG. 8 , showing the filter core expanded. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIGS. 1 and 2 , an air filter in accordance with the present invention comprises a housing  10 , a filter core  20 , a resilient abutting element  30 , a sleeve  40 , a threaded rod bracket  50 , a threaded rod  60 , a nut  70 , and a spacer  80 . 
     With reference to  FIGS. 1 to 3 , the housing  10  has an accommodating space, an inlet  11 , an outlet  12 , a first stepped surface  13 , and a second stepped surface  14 . The inlet  11  and the outlet  12  communicate with the accommodating space. The first stepped surface  13  and the second stepped surface  14  are formed annularly around an inner wall of the housing  10 . The second stepped surface  14  is disposed between the first stepped surface  13  and the outlet  12 . An inner diameter of an inner periphery of the second stepped surface  14  is smaller than an inner diameter of an inner periphery of the first stepped surface  13  as shown in  FIG. 3 . In a preferred embodiment, an inner diameter of the housing  10  remains unchanged from the first stepped surface  13  to the inlet  11 . A fixing bracket  15  is mounted securely on an outer wall of the housing  10 , is made of a bent elongated sheet, and has two elongated holes  151  formed through the fixing bracket, thereby facilitating convenience in assembling the fixing bracket on another object. 
     The filter core  20  is mounted in the accommodating space of the housing  10  and has two axial end surfaces and a through hole  26 . The through hole  26  is formed axially through a center of the filter core  20 . With reference to  FIGS. 6 and 7 , the filter core  20  has a wavy filtering sheet  22 , a flat filtering sheet  21 , multiple adhesives  25 , and two end sealing adhesive layers  24 A,  24 B. The wavy filtering sheet  22  and the flat filtering sheet  21  are for filtering suspended pollutants, are rolled into a cylinder, and are alternately stacked to form multiple layers of the wavy filtering sheet  22  and layers of the flat filtering sheet  21 . Thus, two surfaces of each layer of the wavy filtering sheet  22  are respectively flush with two adjacent layers of the flat filtering sheet  21 . Multiple channels  23 A,  23 B are formed between each layer of the wavy filtering sheet  22  and the two adjacent layers of the flat filtering sheet  21 A,  21 B. The adhesives  25  are respectively spread on the two surfaces of each layer of the wavy filtering sheet  22 , and are respectively and axially spread along peaks of the surfaces of said layer of the wavy filtering sheet  22 , to be respectively adhered securely with the two adjacent layers of the flat filtering sheet  21 A,  21 B. One of the end sealing adhesive layers  24 A is adhered between each layer of the wavy filtering sheet  22  at the side adjacent to the inlet  11  and one of the layers of the flat filtering sheet  21 A that are adjacent to said layer of the wavy filtering sheet  22 . Thus, the channels  23 A between said layer of the wavy filtering sheet  22  and said layer of the flat filtering sheet  21 A are sealed at the side adjacent to the inlet  11 . The other end sealing adhesive layer  24 B is adhered between said layer of the wavy filtering sheet  22  at the side adjacent to the outlet  12  and the other layer of the flat filtering sheet  21 B that is adjacent to said layer of the wavy filtering sheet  22 . Thus, the channels  23 B between said layer of the wavy filtering sheet  22  and said layer of the flat filtering sheet  21 B are sealed at the side adjacent to the outlet  12 . In a preferred embodiment, the adhesives  25  and the end sealing adhesive layers  24 A,  24 B are preferably, but not limited to, hot-melt adhesives or Polyurethane (PU) structural adhesives. The flat filtering sheet  21 A,  21 B and the wavy filtering sheet  22  do not need to be pre-heated when adhered by hot-melt adhesives or Polyurethane structural adhesives, thereby facilitating convenience in manufacturing the filter core  20 . With reference to  FIGS. 3 and 4 , an outer diameter of the filter core  20  is bigger than the inner diameter of the inner periphery of the first stepped surface  13  of the housing  10 , and the filter core  20  protrudes out of the inlet  11  of the housing  10 . 
     With reference to  FIGS. 2 to 4 , the resilient abutting element  30  is annularly formed on a periphery of the end surface of the filter core  20  that is adjacent to the outlet  12 , transversely and axially wraps said periphery as shown in  FIG. 4 , and axially abuts the first stepped surface  13  of the housing  10 . In a preferred embodiment, an outer diameter of the resilient abutting element  30  is smaller than the inner diameter of the housing  10  from the first stepped surface  13  to the inlet  11 , such that a transverse gap is formed between the resilient abutting element  30  and the inner wall of the housing  10  at a position corresponding to the resilient abutting element  30  as shown in  FIG. 4 . In a preferred embodiment, the resilient abutting element  30  is made of Polyurethane directly foaming on the periphery of the filter core  20 . Preferably, a liquid colloid is filled by a mold into gaps between structure fibers of the filtering sheets  21 ,  22  of the filter core  20 , and then the liquid adhesive is solidified to form the resilient abutting element  30 . But the resilient abutting element  30  is not limited by the manufacturing method mentioned above, and also can be made by other manufacturing methods or other resilient materials, such as rubber and silica gel. In a preferred embodiment, an axial thickness of the resilient abutting element  30  protruding out of the end surface of the filter core  20  that is adjacent to the outlet  12  ranges, but is not limited to, from 5 mm to 10 mm, preferably 5 mm, and is not altered with variations of the outer diameter or an axial length of the filter core  20 . In a preferred embodiment, a transverse thickness of the resilient abutting element  30  protruding out of an outer wall of the filter core  20  is, but not limited to, 2.5 mm, and is not altered with variations of the outer diameter or the axial length of the filter core  20 . 
     With reference to  FIGS. 2, 3 and 5 , the sleeve  40  is mounted in the through hole  26  of the filter core  20 , and is adhered to a hole wall of the through hole  26 . Two ends of the sleeve  40  are respectively aligned with the end surfaces of the filter core  20 . 
     With reference to  FIGS. 2 and 3 , the threaded rod bracket  50  is mounted securely in the accommodating space of the housing  10 , and is disposed between the filter core  20  and the outlet  12 . In a preferred embodiment, the threaded rod bracket  50  is an elongated sheet, and two ends of the elongated sheet are bent toward the outlet  12  to be axially welded securely to the second stepped surface  14  of the housing  10 . A gap is formed between a middle of the elongated sheet and the filter core  20 . 
     With reference to  FIGS. 2, 3 and 5 , the threaded rod  60  is welded securely to a middle of the threaded rod bracket  50 , is axially mounted through the sleeve  40 , and protrudes out of the end of the sleeve  40  that is adjacent to the inlet  11 . In a preferred embodiment, outer threads  61  of the threaded rod  60  are formed only on a part of an outer wall of the threaded rod  60  that is adjacent to the end of the threaded rod  60 , rather than all over the outer wall of the threaded rod  60 . 
     The nut  70  is mounted around and is screwed on the threaded rod  60 , axially abuts the sleeve  40  in a direction toward the outlet  12 , such that the resilient abutting element  30  axially and tightly abuts the first stepped surface  13  of the housing  10  via the sleeve  40  and the filter core  20  to axially seal a gap between the first stepped surface  13  and the filter core  20  as shown in  FIG. 4 . 
     The spacer  80  is mounted around the threaded rod  60  and is axially clamped between the nut  70  and the corresponding end of the sleeve  40 . In a preferred embodiment, outer diameters of the nut  70  and the spacer  80  are both slightly bigger than an outer diameter of the sleeve  40 , but the nut  70  and the spacer  80  do not block the channels  23 A,  23 B of the filter core  20 . 
     With reference to  FIGS. 2 and 3 , when the air filter of the present invention is assembled, the threaded rod bracket  50  and the threaded rod  60  are mounted securely in the housing  10  first. Then, the filter core  20 , which has been assembled with the sleeve  40  and the resilient abutting element  30 , is mounted in the housing  10  from the inlet  11 , and is mounted around the threaded rod  60  at the same time. Since the outer diameter of the resilient abutting element  30  is smaller than the inner diameter of corresponding position of the housing  10  as shown in  FIG. 4 , the filter core  20  can be put into the housing  10  easily and smoothly. Afterwards, the spacer  80  and the nut  70  are assembled on the sleeve  40 , and the nut  70  is rotated and tightened. Then the assembling of the air filter is completed. The air filter is easy to be assembled. In particular, the nut  70  not only allows easy application of the user&#39;s manual force for rotation, but also can be rotated by an electric tool, which enhances the efficiency of the assembling. 
     With reference to  FIGS. 3 to 5 , the nut  70  abuts the sleeve  40  when rotated, and the sleeve  40  is moved with the filter core  20  and the resilient abutting element  30 , thereby making the resilient abutting element  30  axially and tightly abut the first stepped surface  13 . Thus, the gap between the filter core  20  and the first stepped surface  13  can be effectively sealed as shown in  FIG. 4 , which ensures that the air entering the housing  10  from the inlet  11  will enter the filter core  20 . In addition, the outer diameter of the filter core  20  is bigger than the inner diameter of the inner periphery of the first stepped surface  13 , such that the filter core  20  may abut the resilient abutting element  30  tightly on the first stepped surface  13 . 
     With reference to  FIGS. 3 and 5 , in addition, since the nut  70  only abuts the sleeve  40 , and the threaded rod bracket  50  does not need to abut the filter core  20 , the axial end surfaces of the filter core  20  are almost completely unblocked, thereby ensuring that air can smoothly pass through the filter core  20 . 
     With reference to  FIG. 3 , moreover, since two ends of the threaded rod bracket  50  axially abut the second stepped surface  14 , the threaded rod bracket  50  may be supported in an axial direction, which further strengthens the supporting of the threaded rod  60 . 
     Nevertheless, when the filter core  20  is disassembled, since the filter core  20  protrudes out of the inlet  11  of the housing  10 , the user can directly hold the filter core  20 , which makes it easy for the user to apply force on and take out the filter core  20 . 
     With reference to  FIG. 1 , the air filter of the present invention may be used in an air compressor or a diesel engine. When the air filter is in use, the air to be filtered directly enters the filter core  20 , which protrudes out of the inlet  11  of the housing  10 . With reference to  FIGS. 6 and 7 , the air enters the channels  23 B, which are not sealed in the end surface of the filter core  20  that is adjacent to the inlet  11 . Then, when the air moves in the channels  23 B to the other end surface of the filter core  20 , the air is blocked by the end sealing adhesive layer  24 B. Consequently, the air passes through the wavy filtering sheet  22  to the other channels  23 A, and then flows out of the filter core  20  to arrive at the outlet  12 . When the air passes through the wavy filtering sheet  22 , the wavy filtering sheet  22  filters the suspended particles from the air to clean the air. In addition, the air may pass through the flat filtering sheet  21 B to arrive at another channel, and the flat filtering sheet  21 B also can filter the suspended particles from the air. 
     Since the adhesives  25  are spread on both surfaces of the wavy filtering sheet  22 , and are axially spread along the peaks of the wavy filtering sheet  22 , the adhered area between the wavy filtering sheet  22  and the flat filtering sheet  21  is large enough, and thus the connection between the filtering sheets  21 ,  22  is strong enough. Therefore, no matter in use, wherein the air to be filtered enters the filter core  20  from the inlet  11 , or in a filter core  20  cleaning situation, wherein the clean air enters the filter core  20  from the outlet  12 , the wavy filtering sheet  22  and the flat filtering sheet  21  do not separate from each other, and do not axially protrude out along the direction of the air flow. 
     In addition, the adhesives  25  are axially spread along the peaks of the wavy filtering sheet  22 , thereby preventing spaces of the channels  23 A,  23 B from being occupied by the adhesives  25  to further avoid interfering with the air flow. 
     With reference to  FIG. 3 , furthermore, with the resilient abutting element  30  axially abutting the periphery of the filter core  20  and the nut  70  axially abutting the sleeve  40 , which is adhered with the filter core  20 , both the resilient abutting element and the nut assist with preventing the wavy filtering sheet  22  and the flat filtering sheet  21  from separating from each other and axially protruding out. 
     In another embodiment, the filter core may be replaced by filter cores of other kinds, such as a filter core with adhesives spread not along the peaks but in other manners. In this situation, the embodiment also has the advantages of preventing the axial end surfaces of the filter core from being blocked. 
     In another embodiment, the outer diameter of the resilient abutting element may be equal to the inner diameter of the housing at a position corresponding to the resilient abutting element, thereby transversely supporting the resilient abutting element and the filter core firmly. 
     In another embodiment, the filter core may not protrude out of the inlet of the housing, and the housing further has a first housing and a second housing. The first and second housings are assembled together to form the accommodating space, and the filter core is mounted in the accommodating space. 
     In another embodiment, the housing may not have the second stepped surface, and the threaded rod bracket is transversely mounted securely on the inner wall of the housing. 
     In another embodiment, the threaded rod bracket may not be a bent elongated sheet but is of a different structure, as long as the threaded rod bracket can be mounted with and support the threaded rod. 
     Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.