fig1 shows an inlet valve for a central vacuum cleaning system according to the present invention . the inlet valve includes a main body 10 with an air inlet passageway 12 ending in an outlet spigot pipe connection 14 on a rear face of the main body 10 . the main body defines an air passageway through the main body as shown . an outer door 16 is hinged along a top edge of the main body 10 to permit the outer door 16 to pivot between an open and a closed position and includes door spline walls 18 at each side edge . these door spline walls 18 slide through an opening between low debris walls 20 in the main body as the outer door opens and closes . the door spline walls 18 help to define a front opening on the air passageway through the main body to , among other things , more precisely focus the suction . a cam opening 22 is formed in each door spline wall 18 . a button latch assembly 24 is mounted to the outer door 16 and accessible through an opening 26 . the button latch assembly 24 interacts with a latch mechanism 28 on the main body 10 . also shown is an inner door 30 . the inner door 30 includes a cam follower 32 at each side edge which fits into the cam openings 22 in the door spline walls 18 of the outer door 16 . the inner door 30 also includes a flat gasket 34 to seal against the main body 10 . most preferably the flat gasket 34 is an overmolded gasket which is secured in openings ( not shown ) within the inner door 30 such that the flat gasket 34 projects on both the outside and the inside of the inner door 30 . the outside face of the flat gasket is herein indicated with number 36 . most preferable the flat gasket 34 provides a sealing surface to seal against a sealing edge 38 on the main body 10 when the inlet valve is not in use but there is suction in the system because some other outlet is in use . the inner door 30 also carries a contour molded gasket 40 to seal the air passageway through the body when the inlet valve is in use to prevent a loss of vacuum around the inner door 30 . the operation of these elements will be explained in more detail below . the inner door 30 is pivotally hinged to the main body 10 in a manner described in more detail below . turning now to fig2 , the outer door 16 has outer door hinges 42 by which it can be hingedly mounted to the main body 10 . the inner door 30 is mounted to the main body 10 by means of inner door pivot points 44 , which define an inner door hinge axis . inner door pivot points 44 are mounted into holes 46 in the main body 10 . as well inner door spring cam shafts 48 fit into curved slots 50 on the main body 10 . the inner door 30 is provided with door guide pads 52 ( see fig5 ) located on an outer face 54 of the inner door 30 to ensure that the outer door 16 slides smoothly and without catching across the inner door 30 when the doors are being opened or closed . the cam followers 32 of the inner door 30 fit into the cam openings 22 of the door splines 18 of the outer door 16 . the action of the cam followers 32 is described in more detail below . as shown in fig3 , when the inner and outer doors are opened , they help define an air suction mouth area 56 which leads to a throat area 58 defined over an air foil 60 . as can be seen by the air flow lines f the air flow , created by the suction of the central vacuum motor , is caused to accelerate through the throat area 58 to help lift dirt and debris over the air foil 60 . the air suction area 56 is defined by the inner door lower edge 62 , the outer door splines 18 , and the floor 64 . fig4 shows a view from behind of the preferred form of the invention of fig1 and 2 . in fig4 strengthening ribs 66 , which may be placed in a grid pattern , can be seen on the outer door 16 . as will be appreciated by those skilled in the art , the strengthening ribs 66 provide a rigid plastic door with a lower total amount of plastic than a solid door . therefore the strengthening ribs 66 are useful for stiffening the door without requiring large additional amounts of plastic and provides a material and cost saving feature for the present invention . it will also be appreciated that other rib patterns ( honeycomb ) are comprehended by the present invention . it will also be appreciated that as the inner door 30 is making the sealing connection with the inlet opening of the main body 10 , the outer door 16 can have a more relaxed dimensional tolerance than the inner door 30 . a spring assembly is used to bias the inner and outer doors to an open position . as shown , there are provided the following support elements to complete the spring assembly . on the main body 10 there is provided a top wire terminal 68 and a cable trap hole 70 . the guide wall 72 of the main body 10 helps to hold the spring ( not shown ) in place . a lower wire terminal 74 is provided as well . fig4 also shows , in more detail , the air foil 60 . the throat area 58 is defined by curved walls 76 and the air foil 60 . the purpose of the curved walls 76 is to focus the suction in a region close to the floor next to the sweep inlet valve to encourage the removal of dirt , debris and the like that are swept up to the unit . the air foil 60 helps to encourage efficient removal of debris and sweepings by means of its shape . as well , the outer door hinge 42 is clearly illustrated in fig4 . also shown is the front debris ramp 78 on the main body 10 . a slight incline has been found to provide good results , with the range being between 5 and 20 degrees . the most preferred incline is an 11 degree incline for this embodiment . fig5 discloses the button latch assembly 24 and latch mechanism 28 in exploded view . the button latch assembly 24 is mounted to the outer door 16 and includes a button 80 , with a latch striker 82 , two button springs 84 and 86 , a retainer plate 88 . the latch mechanism 28 is mounted in hole 29 in the main body 10 . the button latch assembly 24 and latch mechanism 28 interact in a known manner to permit the outer door 16 to be held in a closed position , when the latch mechanism 28 holds the latch striker 82 of the button 80 . when the button 80 of the button latch assembly 24 is depressed against the button springs 84 , 86 the latch mechanism 28 releases the latch striker 82 to permit the outer door 16 to spring open to an open position . the back of the latch assembly 28 is best seen in fig4 . it will be appreciated that more or fewer button springs are comprehended by the present invention . the main body 10 is also shown with the inner door 30 and the outer door 16 in exploded view . the outer face 36 of the flat gasket 34 is shown on the inner door 30 to provide reasonable seal between the inner and outer door . this seal is to discourage dirt from getting into the space between the inner and outer doors and potentially disrupting the smooth functioning of the device , while a good seal is desirable it does not need to be airtight . in fact there are breaks in the seal to provide the door guide pads 52 previously described . also shown are the inner door 30 pivot points 44 and the cam follower 32 . fig5 shows the outer door 16 with an opening 26 for the button latch assembly 24 . also shown are the curved walls 76 in the main body 10 which direct the dirt and debris along a specific narrow flow path towards the open throat area 58 defined by the air foil 60 as previously discussed . from the rear ( best seen in fig2 ) it can be seen that the curved walls 76 form a gasket channel or slot 94 which extends in a curved manner from the lower outer corners towards the upper middle . the gasket channel 94 is preferably provided with a rounded lower edge 96 to permit a sliding seal to be made thereagainst . this gasket channel or slot 94 in the front face of the main body 10 accommodates the contour molded gasket 40 . this contour molded gasket 40 is intended to prevent a loss of suction to behind the inner door 30 and so needs to be able to maintain a seal when the inner door 30 is in the fully open position . essentially this contour molded gasket 40 is curved in shape to match the shape of the gasket channel 94 and follows along the contoured sealing edge 38 of the channel 94 of the main body 10 during the rotation of the inner door from the closed to the open position and vice versa . the contour molded gasket 40 is most preferably provided with a face seal to permit better sealing contact with the main body 10 in the open position . as shown on the right hand side of the main body 10 , there is provided wire terminals or contacts 68 and 74 . most preferable the wire terminals 68 , 74 are of the spring loaded type so that wire connections can be easily made to the low voltage wires ( not shown ) without the need for tools or the like . a push nut 100 is provided to hold a plastic grommet 102 in place on the inner door spring cam shaft 48 , when it is located within a curved slot 50 on the main body 10 ( see fig2 ). a door spring 104 is shown with spacer washers 106 , 108 . the spacer washers are preferably electrically conductive and increase the electrical contact area for better reliability . the door spring 104 is held in place and exerts an opening bias on the outer door via the inner door spring cam shaft 48 . the door spring 104 acts on the inner door / outer door combination to cause the doors to open . when the latch striker 82 of the button 80 is held by the latch mechanism 28 the outer door 16 cannot move . when the latch striker 82 is released from the latch mechanism 28 the button latch assembly 24 and thus the outer door 16 to which it is mounted are freed and the door spring 104 causes the doors 16 , 30 to open . as the cam followers 32 of the inner door 30 move along the cam openings 22 , the outer door 16 opens . as the door spring 104 opens the inner and outer doors , the position of the door spring 104 changes relative to the wire terminals 68 , 74 and then , when the doors 16 , 30 are open the door spring 104 closes the electrical contact by contacting the spacer washers 106 , 108 , completing the low voltage circuit , to initiate the central vacuum motor and creating suction . it will be understood by those skilled in the art that the door spring 104 can be exerting force on the inner door 30 , the outer door 16 or both depending upon the configuration of the elements . however , good results have been obtained where the door spring 104 acts on the inner door spring cam shafts 48 of the inner door 30 and the outer door 16 is moved open as the inner door 30 opens . the present invention is also directed to a design which completely covers the vacuum opening when not in use presenting a clean , finished appearance in fig6 the outer face 110 of the outer door 16 is shown with the button 80 . as can be appreciated , the outer face 110 of the present invention presents a clean , finished appearance . as shown , the outer face 110 presents a smooth cover or exterior ( which may be textured if desired ) that will blend easily into wall boards or the like without leaving a gaping opening as in some of the prior art . further while the button 80 is slightly proud of the front surface it can be gently curved or rounded to provide an easy to activate element ( best seen in fig1 ). fig7 shows a further view of the present invention with the outer door 16 removed for ease of illustration . in this view , the outer door hinge pins 112 are shown running across the top of the main body 10 for coupling the outer door hinge 42 . the outer door hinge pins 112 are mounted between pairs of hinge pin support columns 114 . the outer door hinge pins 112 , outer door hinges 42 , and hinge pin support columns 114 form hinge assemblies . it will also be appreciated that each hinge assembly is in the nature of a snap fit coupling of the outer door hinge 42 onto the outer door hinge pin 112 on the main body 10 . in this way the outer door 16 can be removed from the main body 10 for ease of installation or service of the device in a base board or toe rail or the like ( not shown ). in fig7 the mounting screw holes 116 and 118 for the main body 10 are clearly shown and well exposed when the outer door 16 is removed for ease of access . a second set of holes 120 , 122 can also be provided . most preferably , the outer door 16 will be disengaged from the inner door 30 in the shipped form of the invention . the installer simply removes the device from the package , positions the unit on the mounting surface , connects the vacuum piping , and screws the main body 10 in place . afterwards , the outer door 16 can be pressed closed , and there is enough play in the components to allow the cam followers 32 to press past the edge of the door spline walls 18 until they engage in the cam openings 22 . this is achieved by gently pressing the outer door 16 down onto the inner door 30 . in this way installation is quickly and easily completed . as well , fig7 shows the width of the suction opening or chute opening 124 . also shown are lower debris walls 20 which are low walls adjacent to the slots 126 through the main body 10 which house the door spline walls 18 of the outer door 16 . the debris lower debris walls 20 are simply to make it less likely that debris will become jammed into the slots 126 affecting smooth opening and closing of the inner and outer doors 30 , 16 . the connection of the invention to the vacuum piping is established in a conventional manner by placing a vacuum piping connector over the outlet spigot pipe connector 14 which is dimensioned to make a snug fit . glue can be used if desired to complete the joint . in some installations there may be less room behind the invention to establish the connection to the vacuum piping . the present invention provides a short cut line 128 ( see fig1 ) molded into the outlet spigot pipe connector 14 . the short cut line 128 can be used by the installer to reduce the length of the outlet pipe spigot connector 14 to reduce the depth of the invention to accommodate smaller installation spaces . the operation of the present invention can now be more clearly understood . when the outer door 16 is in a closed position it is held in the closed position by means of the interaction between the button latch assembly 24 and the latch mechanism 28 . the flat gasket 34 is in contact with the edge of the main body 10 to maintain a seal all the way along the upper edge . the front 36 of the lower part of the flat gasket 34 on the inner door 30 seals a lower edge of the front of the vacuum opening . a user , who wishes to open the inlet valve of the present invention , simply taps the button 80 with their toe , causing the latch mechanism 28 to release the latch striker 82 thereby allowing the outer door 16 to spring open under the influence of door spring 104 . it will be appreciated that the door spring 104 continuously urges the doors 16 , 30 into an open position , but is frustrated when the interaction of the button latch assembly 24 with the latch mechanism 28 latches the outer door 16 in a closed position . in other words , upon release of the button latch assembly 24 from the latch mechanism 28 , the outer door 16 is allowed to move to an open position by means of the door spring 104 acting on inner door spring cam shaft 48 on the inner door 30 . as shown in fig8 a when the doors are closed the cam follower 32 is located at a lower end of the cam opening 22 . as shown the cam follower 32 is in the form of a shaped post , with a lower outer curved surface that fits against the curved cam opening 22 at position 130 . as shown in fig8 b , with the doors open the cam follower 32 is now located towards the other end of the cam opening 22 at position 132 . the shape of the cam opening 22 is due to the inner door hinge axis being displaced from the outer door hinge axis . this results in a need to have the cam follower 32 move along an arc , relative to the outer door 16 , requiring the cam opening 22 to have a curved shape . as the inner door 30 is urged outwardly , the outer door 16 is also pivoted about its hinge points and opens the air suction area 56 of the inlet valve . as the inner door 30 pivots open the flexible contour molded gasket 40 moves within the gasket channel 94 allowing the inner door 30 to change position without binding during opening and closing . in this way , when opened , the contour molded gasket 40 seals on sealing edges 38 and the sweepings are directed only through the throat of the unit and not into any other spaces . as the door spring 104 moves to the open door position , it closes a low voltage circuit between the wire terminals 68 , 74 initiating the vacuum motor and suction through the main body 10 . as will now be appreciated , the main body 10 includes curved walls 76 which feed to a throat area 58 defined by an air foil 60 . as a result , the suction is directed , concentrated and the air flow maintained at an optimum speed to help the present invention achieve superior suction and hence removal of the debris located within the general area of the air suction area 56 of the inlet valve . when the debris swept up to the unit has been sucked away , the user can simply push on the button 80 with their toe to cause the outer door 16 to close . this will close the inner door 30 , load up the door spring 104 and disengage the door spring 104 from the wire terminals 68 , 74 causing the central vacuum motor to shut down . as the outer door 16 reaches the fully closed position the latch mechanism 28 will again engage and hold the doors 16 , 30 in a closed position against the biasing force of the now reloaded door spring 104 . in some cases the inner door 30 might not be held closed onto the main body 10 , due to design tolerances of the plastic molded parts . however , even so the inner door 30 is able to retain suction because the activation of suction in the system , for example when another inlet valve is in use , will cause the inner door 30 to be sucked onto the sealing edges 38 of the main body 10 creating a tight seal and preventing a loss of suction . while the foregoing mode of latching and unlatching of the doors is the most preferred form of the invention , the present invention also comprehends that an electronic switch such as a solenoid or rf activated remote controlled switch , or even a buttonless door latch , can be used in place of the button latch assembly 24 and latch mechanism 28 discussed above . a buttonless alternative embodiment of the present invention is shown in fig9 and 10 . in this embodiment the whole door acts as the button , and so no separate button is required . in fig9 and 10 like elements from the first embodiment are shown with like numbers . in this embodiment the latch striker 134 extends rearwardly from the outer door 16 as shown . to achieve a balance of forces on the doors , a passive flat spring 136 is mounted in a recess 138 and contacts the outer door 16 in a generally symmetrically disposed position to said latch striker 134 . the flat spring 136 is sized and shaped to allow the forces along the outer door to be evenly balanced to permit smooth operation of the doors . in this embodiment , a user simply taps on the door , in any location , to cause the latch striker 134 to be released from the latch mechanism 28 . once released this embodiment functions the same as previously described , with the door spring 104 opening the device . to close the outer door 16 , the user simply presses on the outer door 16 in any location to cause the outer door 16 to close and the latch striker 134 to be captured by the latch mechanism 28 . although it would be preferable to position the latch striker 134 in the middle of the door 16 , the air inlet passage way 12 and inner door 30 are in the way . therefore , the present invention provides a latch striker 134 / latch mechanism 28 on one side of the unit , with the flat spring 136 on the other side . as can now be appreciated the present invention provides a sleek unit , able to fit into small installation spaces and yet which provides a wide suction mouth area . without limiting the invention to these dimensions , a preferred form of the unit is 299 . 7 mm long by 91 . 4 mm tall by 69 mm thick . the air suction area 56 is 216 mm wide at the floor 64 . it will also be appreciated that the present invention can be installed in a wall , or in a floor although the latter is believed less preferred as it creates a potential tripping hazard when the unit is open and in use . it will be appreciated that the foregoing description is in respect of certain preferred embodiments of the present invention , but that other configurations are comprehended within the broad ambit of the appended claims . some of these alterations and variations are discussed above and others will be apparent to those skilled in the art . for example , although in the preferred embodiment the door spring 104 acts on the outer door 16 , this is not essential . all that is required is for the inner and outer doors to be motivated by the door spring 104 so that when released the doors open , the electrical circuit is completed and the vacuum motor can start .
an inlet valve for a central vacuum cleaning system having a central vacuum motor connected to a piping network , is disclosed . the inlet valve includes a main body having an air inlet passageway formed therethrough and a pipe connector to connect the air inlet passageway of the inlet valve to the vacuum piping . an outer door is provided which is pivotally mounted to the main body on an opposite side to said connector and an inner door is provided which is pivotally mounted to said main body at one end between the outer door and the main body and seals the air inlet passageway when the inner door is in a closed position . a releasable latch is operatively connected to the outer door to keep the outer door and the inner door closed on the front of the valve when the inlet valve is not in use and a spring is provided to cause the inner door and the outer door to open upon the latch being released .