Abstract:
A central vacuum system includes a cylindrical canister with a slide-out filter drawer that can be used either in a filtered or cyclonic vacuum system. The drawer permits servicing the filter without having to otherwise open the canister. The dirtier upstream side of the filter element faces downward to help prevent dust from piling up on the filter element.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The subject invention generally pertains to central vacuum systems and more particularly to a filter for such a system.  
         [0003]     2. Description of Related Art  
         [0004]     Typical central vacuum systems comprise a blower or vacuum motor that creates a vacuum within a stationary canister. A network of tubing usually connects the canister to several wall-mounted inlet ports that are installed at various locations throughout a house or building. A flexible hose can connect a portable vacuum tool to any of the inlet ports, so the tool can be used for vacuuming a floor. The vacuum motor draws dust-laden air in series through the tool, through the hose, through the tubing network and into the canister where the dust collects. The canister can be manually opened to empty it periodically.  
         [0005]     There are two main types of central vacuum system: cyclonic and filtered. With a cyclonic system, structure within the canister directs the dust-laden air to circulate in a vortex, which employs centrifugal force to help separate the heavier dust particles from the air. A chute directs the separated dust particles to the bottom of the canister where they accumulate for later disposal. The vacuum motor draws the lighter clean air out from within the center of the vortex and discharges the air to atmosphere. Some cyclonic vacuum systems also include a filter, but that is not necessarily always the case.  
         [0006]     In comparison, a filtered system includes a filter instead of the vortex-generating structure. The filter blocks the dust particles while allowing clean air to be discharged to atmosphere. If the filter is in the form of a bag, the dust collects in the bag. Otherwise, the dust may simply drop from the filter onto the bottom of the canister. With a filter system, the canister is emptied by first opening the canister and then manually removing the dust from within the bag and/or from the bottom of the canister.  
         [0007]     In addition to a canister&#39;s main system for separating and collecting the dust, the canister may include a smaller, secondary filter for ensuring that the air is truly clean before being discharged from the canister. This is particularly important in cases where the vacuum motor discharges the air back into the house rather than discharging it outdoors.  
         [0008]     Opening the canister of a central vacuum system to dispose of the collected dust is a dirty job. Since the canister typically serves an entire house, the canister can be quite large and bulky, and it can hold a lot of dirt. Thus, it may seem impractical to open a rather large dirty canister just to occasionally clean, inspect, or replace a filter. Thus, there is a need for an easier, cleaner way of accessing the filter.  
         [0009]     Various designs have been developed for changing vacuum filters. U.S. Pat. No. 5,230,722, for example, discloses a portable vacuum cleaner whose filter is changed via a slide-out filter tray. Although the filter may be easy to service, it has some limitations.  
         [0010]     One, the airflow passes through the filter is a downward direction, which may work for a portable vacuum system. With a central vacuum system, however, the vacuum motor is typically mounted near the top of the canister, so the lower end of the canister is available for collecting dust. Thus, the downward airflow pattern through the filter of the &#39;722 patent is not readily adapted for use on conventional central vacuum systems.  
         [0011]     Two, with a downward airflow pattern, dust can pile up or accumulate on top of the filter. The accumulation of dust can obstruct the volume of airflow through the filter, thereby diminishing the overall effectiveness of the vacuum system.  
         [0012]     Three, having a drawer opening in a relatively small, portable vacuum cleaner may be fine; however, a drawer penetrating the cylindrical sidewall of a larger diameter central vacuum canister may weaken the canister, which is subject to a potentially crushing pressure differential.  
         [0013]     Four, the filter tray of the &#39;722 patent offers no way of creating a seal between an upper surface of the filter element and an upper air passageway leading to the vacuum motor of a conventional central vacuum canister. Without such a seal, air traveling to the vacuum motor could bypass the filter.  
         [0014]     Consequently, a need exists for a more convenient way of servicing a secondary filter of a central vacuum system.  
       SUMMARY OF THE INVENTION  
       [0015]     One object of some embodiments of the invention is to provide a cylindrical canister of a central vacuum system with a slide-out filter drawer.  
         [0016]     Another object of some embodiments is to provide a central vacuum system with a way of servicing the system&#39;s secondary filter without having to interfere with the system&#39;s main dust-collecting receptacle.  
         [0017]     Another object of some embodiments is to provide the canister of a central vacuum system with a drawer filter that is held in place with the assistance of a vacuum created within the canister.  
         [0018]     Another object of some embodiments is to provide a filter and drawer assembly where an upstream surface of the filter faces downward so that dust obstructed by the upstream surface may eventually fall away from the filter and accumulate elsewhere.  
         [0019]     Another object of some embodiments is to provide a filter drawer that permits air to pass through and around the drawer, thereby taking greater advantage of the filter&#39;s surface area by allowing air to enter both the bottom and side surfaces of the filter.  
         [0020]     Another object of some embodiments is to provide a filter drawer that permits air to pass through and around the drawer, yet still reinforces the drawer-penetrated canister of a central vacuum system.  
         [0021]     Another object of some embodiments is to provide a slide-out filter drawer for various types of central vacuum systems including, but not limited to, filtered and cyclonic systems.  
         [0022]     Another object of some embodiments is to provide a gasket between a filter drawer and an air passageway leading to a vacuum motor.  
         [0023]     Another object of some embodiments is tilt a filter element at an angle relative to the horizontal movement of a drawer that supports the filter, so the drawer upon being inserted in the canister wedges the filter sealingly up tight against an air passageway.  
         [0024]     One or more of these and/or other objects of the invention are provided by a central vacuum canister that includes a slide-out filter drawer.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]      FIG. 1  is a cross-sectional side view of a vacuum canister and a schematic illustration of the remainder of a central vacuum system, wherein the canister includes a filter drawer shown in its inserted position.  
         [0026]      FIG. 2  is a cross-sectional view of the canister of  FIG. 1  but showing the filter drawer in its retracted position.  
         [0027]      FIG. 3  is a perspective view of a canister with its filter drawer in its retracted position and its associated filter element retracted.  
         [0028]      FIG. 4  is a cross-sectional top view taken along line  44  of  FIG. 1  with a portion of the filter element cutaway.  
         [0029]      FIG. 5  is a cross-sectional view similar to  FIG. 1  but showing another type of central vacuum canister.  
         [0030]      FIG. 6  is a cross-sectional view similar to  FIGS. 1 and 5  but showing yet another type of central vacuum canister. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]     Referring to  FIGS. 1-4 , a canister  10  for a central vacuum system  12  includes a slide-out filter drawer  14  that facilitate the servicing of a filter element  16 .  
         [0032]     Central vacuum system  12  comprises a vacuum motor  18  (i.e., a blower) whose fan inlet  20  creates a vacuum in canister  10 . A suction pipe  22  connects the vacuum in canister  10  to a network of tubing  24 , which leads to several wall-mounted inlet ports  26  that are installed at various locations throughout a house  28  or building. A flexible hose  30  connects a portable vacuum tool  32  to any of the inlet ports  26 , so tool  32  can be used for vacuuming a floor  34  or other surfaces.  
         [0033]     Vacuum motor  18  draws dust-laden air  36  in series through tool  32 , through hose  30 , through tubing network  24  and into canister  10  where much of the dust collects within a main filter bag  38 . A joint connector  40  enables canister  10  to be manually opened to change the main filter bag or empty the canister periodically. Although, in this example, the air and dust are separated by filtration and the dust is collected within a filter bag, other methods of separation and collection are well within the scope of the invention. After separating dust from the air, vacuum motor  18  discharges cleaner air  36 ′ through an outlet pipe  42  that exhausts the air to atmosphere.  
         [0034]     To ensure that the air discharged to atmosphere is truly clean and to avoid occluding vacuum motor  18  with dust, drawer  14  positions filter element  16  just upstream of fan inlet  20 . To accomplish this structurally, a divider  44  divides canister  10  between an upper section  46  and a lower section  48 . Divider  44  includes a rim  50  that defines an air passageway  52  leading to fan inlet  20 . Drawer  14  holds filter element  16  such that upon inserting drawer  14  into canister  10 , a set of tracks  54  guide drawer  14  where the drawer can force an upper surface  56  of filter element  16  up against rim  50 . Upper surface  56  may include an annular gasket  58  to ensure a positive seal between rim  50  and filter element  16 . Alternatively, annular gasket  58  could be part of or attached to rim  50 , whereby a gasket portion of rim  50  would engage an upper surface of filter element  16 .  
         [0035]     It should be noted that air passing upward through filter element  16  creates a pressure differential across the filter. Although the pressure differential may exert a significant upward force against filter element  16 , that force is counteracted by filter element  16  abutting rim  50  of divider  44 . Since it is divider  44 , and not drawer  14  and track set  54 , that provides the reactive force, drawer  14  and track set  54  can be made lighter and less expensive.  
         [0036]     To inspect, clean or replace filter element  16 , drawer  14  may be manually moved between an inserted position of  FIG. 1  and a retracted position of  FIG. 2 .  FIG. 3  shows how easily filter element  16  can be replaced. The new replacement filter element is simply inserted into a pocket  60  of drawer  14 .  
         [0037]     The actual structure of drawer  14 , filter element  16 , track set  54 , and divider  44  may vary; however, in a currently preferred embodiment, filter element  16  and rim  50  are tilted at an angle  62  (beyond 90-degrees) relative to a longitudinal centerline  64  of canister  10 . Angle  62  ensures that filter element  16  is pressed up against rim  50  when drawer  14  is inserted. Angle  62  also aids in removing drawer  14 , as filter element  16  does not have to be dragged continuously across rim  50  as drawer  14  is retracted. In a currently preferred embodiment, angle  62  is achieved by having a filter-supporting ledge  66  of drawer  14  being set at angle  62 .  
         [0038]     In some cases, drawer  14  includes a cover plate  68  that sealingly covers a drawer opening  70  in canister  10 . A seal  72  can help close any gaps that may otherwise exist between cover plate  68  and canister  10 . A conventional door latch (not shown) and/or canister vacuum acting upon cover plate  68  can help hold cover plate  68  snugly against canister  10  and/or seal  72 . It should be appreciated by those of ordinary skill in the art that such a latch or some other closing mechanism may help in sealing the canister so that vacuum motor  18  can initiate a vacuum in the canister. When cover plate  68  is part of drawer  14 , rather than being a separate item, the means for holding cover plate  68  shut can be the same means that holds filter element  16  up against rim  50 .  
         [0039]     The relative translating motion between drawer  14  and track  54  can be accomplished in countless ways. Track  54 , for instance, can be a channel in which the drawer&#39;s lateral edges  74  slide. Or, the drawer&#39;s lateral edges could be in the form of a channel that engages an edge of the tracks. Track  54  could also be an angle or some other structure that provides a ledge upon which drawer  14  slides. The guided translating motion between a drawer and track can also be provided by a linear bearing that may include roller elements.  
         [0040]     Filter drawer  14  can help reinforce canister  10  in the area of drawer opening  70 . When a vacuum exists inside canister  10 , the canister is subjected to an exterior-to-interior pressure differential that applies a compressive force against canister  10 . Drawer  14  can help oppose that compressive force by having track set  54  and drawer  14  installed as shown in  FIG. 4 . More specifically, brackets  76  fasten track set  54  to the inner wall of canister  10  so that brackets  76  and track set  54  transfer the compressive forces (acting on the exterior wall of canister  10 ) to lateral edges  74  and into drawer  14  itself.  
         [0041]     Filter element  16  can be of any suitably porous material, such as foam, pleated paper, etc. To make the most use of the filter element&#39;s surface area, drawer  14  defines an opening  78  through which the air can pass prior to passing through a lower surface  80  of filter element  16 . In cases where filter element  16  has an outer perimeter  82  that is also porous, the air can pass around drawer  14  through air gaps  84  and enter perimeter  82 . Thus, air can pass through both lower surface  80  and perimeter  82  before passing out through an upper surface  86  of filter  16  and entering fan inlet  20 .  
         [0042]     In some cases, lower section  48  of canister  10  comprises a drawer-supporting section  88  and a dust-collecting section  90 , wherein filter element  16  can be contained within drawer-supporting section  88 , and dust-collecting section  90  is removable (via fasteners  40 ) out from underneath drawer-supporting section  88  to dispose of collected dust in the canister.  
         [0043]     Slide-out filter drawer  14  can be used in a wide variety of central vacuum systems.  FIG. 5 , for instance, shows a canister  92  whose main filter  94  is installed above suction pipe  22 . De-energizing vacuum system  96  allows some of the dust, which was obstructed by filter  94 , to fall back down to the bottom of canister  92 , where the dust collects in a pile  98  for later disposal.  
         [0044]     Filter drawer  14  can also be used in a cyclonic central vacuum system  100 , as shown in  FIG. 6 . System  100  includes a canister  102  with a vortex-generating cylinder  104 . A suction inlet pipe  22 ′ leading tangentially into canister  102  directs air into a downward circular motion around cylinder  104 . Centrifugal force separates the dust from the air by slinging the heavier dust particles against the interior wall of canister  102 . A funnel  106  then directs the separated dust to the bottom of canister  102  for later disposal. Once the dust is separated from the air, the cleaner air travels up through a central portion of cylinder  104 . From there, the air passes through filter element  16  before vacuum motor  18  discharges the air out through outlet pipe  42 .  
         [0045]     Although the invention is described with reference to a preferred embodiment, it should be appreciated by those of ordinary skill in the art that various modifications are well within the scope of the invention. Filter element  16 , for example, is shown being centered relative to the canister&#39;s longitudinal centerline  64 ; however, the filter element could be radially offset to the centerline to place the filter element closer to the canister&#39;s opening  70 , thereby shortening the required length of the filter element drawer and the track that supports it. Therefore, the scope of the invention is to be determined by reference to the following claims.