Abstract:
A filter assembly includes a filter head with a first thread. The filter head has an inlet port and outlet port. The filter assembly includes a filter bowl including a second thread that screws on and off the first thread between mounted and unmounted positions. A filter element, housed in the filter bowl is in communication with the inlet port and outlet ports. The filter element is disposed along a flow path running from the inlet port to the outlet port. The filter assembly further includes a locking collar having a first catch acting upon a second catch provided by one of the filter head and the filter bowl in order to lock the filter bowl to the filter head in the mounted position. In an embodiment, the catches are adapted to be disengaged to allow rotation of the filter bowl from the mounted position to the unmounted position.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention generally relates to filter assemblies such as those suitable for use in hydraulic systems, particularly aircraft hydraulic systems. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are a number filter systems used in a range of applications where it is necessary to remove impurities from a fluid. Conventional hydraulic systems typically include filter assemblies a filter bowl which houses a filter element. The filter bowl typically attaches to a filter head assembly, which typically includes an input and an output for the flow of hydraulic into and away from the filter element. Some of these conventional systems allow for the removal of the filter bowl to allow for replacement of the filter element when the filter element becomes saturated with impurities. 
         [0003]    The present invention is directed towards improvements over the state of the art, and particularly to the attachment mechanisms between a filter head assembly and filter bowls. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    In one aspect, embodiments of the invention provide a filter assembly that includes a new locking mechanism. The filter assembly includes a filter head with a first thread. The filter head has an inlet port and an outlet port. The filter assembly also includes a filter bowl including a second thread that screws on and off the first thread between a mounted position and an unmounted position, respectively. A filter element, at least partially enclosed by the filter bowl, is in communication with the inlet port and the outlet port. The filter element contains a filter media for filtering fluid. In a particular embodiment, the filter element is disposed along a flow path running from the inlet port to the outlet port. The filter assembly further includes a locking collar having a first catch acting upon a second catch provided by one of the filter head and the filter bowl in order to lock the filter bowl to the filter head in the mounted position. In an embodiment, the catches are adapted to be disengaged to allow rotation of the filter bowl from the mounted position to the unmounted position. 
         [0005]    In another aspect, embodiments of the invention provide a method of attaching a filter bowl assembly to a filter head assembly. The method includes providing a locking mechanism configured to securely attach a filter bowl to a filter head assembly, and providing, during the locking mechanism attachment process, a visual indicator, an audible indicator, and a tactile indicator to indicate that the locking mechanism is properly engaged. In a particular embodiment, such indication that the locking mechanism is properly engaged means that the filter bowl is threaded into the filter head assembly sufficiently to prevent the filter bowl from inadvertently detaching from the filter head assembly such that the filter bowl does not work loose from the filter head assembly by means of aircraft vibration, for example, or other means. 
         [0006]    In yet another aspect, embodiments of the invention provide a filter assembly that includes a filter bowl having a threaded portion, and a filter head assembly having a threaded portion configured to receive the threaded portion of the filter bowl. In a particular embodiment, the filter assembly also includes a collar configured to attach to one of the filter head assembly and the filter bowl. In a more particular embodiment, the collar has a first locking portion configured to engage the other of the filter head assembly and the filter bowl. This engagement is configured to prevent detachment of the filter bowl from the filter head assembly. 
         [0007]    Other aspects, objectives and advantages 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 
         [0008]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0009]      FIG. 1  is a plan view of the filter system with locking mechanism, constructed in accordance with an embodiment of the invention; 
           [0010]      FIG. 2  is a pictorial view of a locking collar spring adapted to be incorporated into an embodiment of the invention; 
           [0011]      FIG. 3  is a pictorial view of a wave spring adapted to be incorporated into an embodiment of the invention; 
           [0012]      FIG. 4  is a pictorial view of a retainer adapted to be incorporated into an embodiment of the invention; 
           [0013]      FIGS. 5A-5C  are exploded assembly views of the filter bowl with components of the locking mechanism showing progressive assembly of the locking collar, according to an embodiment of the invention; 
           [0014]      FIG. 6  is a close-up view of the locking mechanism constructed in accordance with an embodiment of the invention; 
           [0015]      FIGS. 7A-7C  are pictorial views of the filter assembly with locking mechanism showing operational features thereof relating to servicing of the filter assembly as might be done by a mechanic; and 
           [0016]      FIG. 8  is a pictorial view of the filter head assembly of  FIGS. 7A-7C . 
       
    
    
       [0017]    While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIG. 1  is a pictorial view of a filter assembly  100  incorporating a locking mechanism  102  according to an embodiment of the invention. Embodiments of the filter assembly  100  provide an example of the type of filter assembly that might be found in the hydraulic system of an aircraft. However, one of ordinary skill in the art will recognize that filter assembly  100  is not limited to such uses, and could be found in any number of hydraulic systems or could be used for the filtering of fluids other than hydraulic. The locking mechanism  102  serves to secure attachment of filter head assembly  104  to filter bowl assembly  106 . The filter bowl assembly includes filter bowl  107 , and a replaceable filter element  115  having filter media to remove impurities from fluids such as hydraulic or lubricating oil, for example. 
         [0019]    The filter head assembly  104  includes an inlet  108  and an outlet  110 . In a hydraulic system, for example, the hydraulic would flow into inlet  108  through the filter element  115  and filtered hydraulic would out through outlet  110 . In a particular embodiment of the invention, the filter head assembly  104  has a substantially cylindrical portion  112 . In a more particular embodiment, the inner surface of the cylindrical portion  112  is threaded such that the cylindrical portion  112  is configured to receive a threaded portion  109  (shown in  FIG. 5A ) on the filter bowl  107  of the filter bowl assembly  106 . Below the threaded portion  109  on the filter bowl  107 , there is a ledge  111  (shown in  FIG. 5A ) to support the components of the locking mechanism  102 . 
         [0020]    In an embodiment of the invention, the locking mechanism  102  includes collar  120 , a biasing element, which, in the embodiment shown, is wave spring  140 , and retainer  150 .  FIG. 2  is a pictorial view of a collar  120 , constructed in accordance with an embodiment of the invention. In the exemplary embodiment of  FIG. 2 , the collar  120  is substantially cylindrical. At a first  122  end of the collar  120  are one or more catches, which may take the form of a ratchet wheel having teeth  124  disposed circumferentially that end of the collar  120 . In a particular embodiment, a second end  126  of the collar  120  opposite the first end  122  has one or more slotted openings or slots  128  that may be used to provide a detent mechanism for holding the collar in an unlatched position. In a particular embodiment, these slots have a axial leg  130  and a radial leg  132 . One or more detent tabs  113  projecting radially from an outer surface of the filter bowl  107  ride in the one or more slots  128  and can hold the collar  120  in the unlatched position when in the radial leg  132 . 
         [0021]    In particular embodiments, an inner surface of the collar  120  includes an annular lip  134  that projects radially inward. The lip interacts with other components of the locking mechanism  102  to keep the components in place. In particular embodiments, the collar  120  may be made of metal such as aluminum or steel or alloys thereof, but may also be made from non-metallic materials such as plastic. 
         [0022]      FIG. 3  is a pictorial view of a wave spring  140  which can be incorporated into the embodiment of the invention shown in  FIG. 1  and can serve to bias the collar  120  toward the latched position. In at least one embodiment, the wave spring  140  is made from a spirally wound annular member  142  that contains waves which provide the biasing force. The annular member  142  is configured such that it can be compressed in the axial direction. 
         [0023]    In embodiments of the invention, the wave spring  140  is made from a resilient, yet sufficiently rigid material such as stainless steel, aluminum, or alloys thereof. However, it is also envisioned that suitable non-metal materials including certain plastics and composites may be used in some applications. 
         [0024]      FIG. 4  is a pictorial view of a retainer  150  which can be incorporated into the embodiment of the invention shown in  FIG. 1 . In a particular embodiment, the retainer  150  is annular. At one end  152  of the retainer, a lip  154  projects radially outward. In a particular embodiment, the retainer  150  is made from aluminum, stainless steel or alloys thereof. It is also envisioned that the retainer could be fashioned from a suitable non-metallic material such as plastic or ceramic. In an embodiment, the retainer  150  is press fit, glued, or otherwise fixedly secured to retain the collar  120  in place, while allowing for axial movement of the collar  120  between latched and unlatched positions. 
         [0025]      FIGS. 5A-5C  is an exploded pictorial view of the filter bowl assembly  106  and locking mechanism  102  according to an embodiment of the invention. The filter element is not shown in these figures. However, as can be seen in  FIG. 5B , the wave spring  140  fits onto the filter bowl  107  just below the threaded portion  109 . As shown in  FIG. 5C , the collar  120  is assembled over the wave spring  140  onto the filter bowl assembly  106 . The retainer  150  is inserted between the wave spring  140  and filter bowl  107 . 
         [0026]      FIG. 6  illustrates a close-up view of the locking mechanism  102 . The wave spring  140  is held in place supported by the ledge  111  of the filter bowl  107  on the bottom, and by the annular lip  134  of the collar  120  on the top. The bottom of retainer  150  is supported by ledge  111 , while the lip  154  of the retainer  150  abuts the annular lip  134  of the collar  120 . The retainer  150  is press fit onto the filter bowl  107 , and serves to keep the wave spring  140  in place. In a particular embodiment of the invention, the filter bowl  107  includes one or more detent tabs  113 , which act as a detent mechanism, configured to fit into the one more slots  128 . 
         [0027]      FIGS. 7A-7C  illustrate the operational modes of the locking mechanism  102 . In a particular embodiment the filter head assembly includes one or more catches that may take the form of teeth  158  configured to mate with the series of teeth  124  on the collar  120 . In at least one embodiment, the series of teeth  124  on the collar  120  are substantially triangular with a ramped surface  160  and a vertical surface  162  such that when the series of teeth  124  on the collar  120  engages the series of catches  158  on the filter head assembly  106 , the ramped surfaces  160  permit rotation of the collar  120 , and therefore the filter bowl assembly  106  in one direction; the direction in which the filter bowl assembly  106  screws into the filter head assembly  104 . The vertical surface  162  prevents the collar  120 , and the filter bowl assembly  106 , from rotating in the opposite direction thus preventing the filter bowl assembly  106  from unscrewing and detaching from the filter head assembly  104 . 
         [0028]      FIG. 7A  shows the locking mechanism  102  engaged with the series of catches  124  on the collar engaged with the series of teeth  158  on the filter head assembly  104 .  FIG. 8  provides a pictorial view of the filter head assembly  104  showing teeth  158 , input  108 , and output  110 . In the embodiment shown in  FIG. 7A , when the locking mechanism  102  is engaged, the detent tab  113  is located at the bottom of the axial leg  130  of the slot  128  (shown in  FIG. 2 ). In the embodiment shown, the collar  120  is slidable in an axial direction. Thus, to disengage the locking mechanism  102 , the collar  120  must be pulled down, as shown in  FIG. 7B , compressing the wave spring  140 , which normally biases the collar  120  into engagement with the filter head assembly  104 . Once pulled down, the collar  120  is rotated, as shown in  FIG. 7C , such that the detent tab  113  is at or near the end of the radial leg  132  of the slot  128 . 
         [0029]    In particular embodiments of the invention, one or more components of the locking mechanism  102  are made to be visually distinctive from surrounding components such that there is an obvious visual indicator when the locking mechanism  102  is not properly engaged. For example, the retainer  150 , or possibly the wave spring  140  could be made in a color easily distinguishable from that of surrounding components. When the locking mechanism  102  is properly engaged, the collar  120  would completely, or nearly completely, cover the retainer  150  and wave spring  140 . Thus, if the easily distinguishable retainer  150  or wave spring  140  is visible, this would indicate to the user that the locking mechanism  102  is not properly engaged. 
         [0030]    In this manner, the one or more detent tabs  113  serve to keep the collar  120  in the lowered position with the wave spring  140  in compression. With the collar  120  disengaged, the filter bowl assembly  106  can be unscrewed so that the filter element can be replace. When the filter element is replaced, the filter bowl assembly  106  is screwed into the filter head assembly  104  and the collar  120  is rotated so that the wave spring  140  urges the series of teeth  124  on the collar  120  into engagement with the series of teeth  158  on the filter head assembly  104 . Because of the arrangement of the mating teeth  124 ,  158 , when the locking mechanism  102  is engaged as described, there is an audible click when the teeth  124 ,  158  snap into alignment, which indicates to the user that the locking mechanism  102  is properly engaged. Further, there is a tactile indicator in that the user will normally be able to feel, as well as hear, the mating teeth  124 ,  158  snap into place. 
         [0031]    While the locking mechanism  102  in the embodiments described above is on the filter bowl  107  with a corresponding structure on the filter head assembly  104 , one of ordinary skill in the art will recognize that the locking mechanism may be configured to be on the filter head assembly  104  with the corresponding structure on the filter bowl  107 . Certain claims appended hereto are meant to encompass both possibilities. 
         [0032]    All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0033]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0034]    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.