Abstract:
A vacuum system has a cabinet that can be mounted to a wall. The cabinet includes a hose connectable to a vacuum source. The hose is extendible from the cabinet between extended and retracted positions. A rotatable shaft drives the hose and a power source causes the rotatable shaft to rotate. A sensor measures the speed of rotation of the shaft and signals a controller to stop the power source when the speed falls below a predetermined threshold.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates generally to vacuum systems, and more particularly to mechanisms for automatically driving vacuum hoses.  
         [0003]     2. Description of the Related Art  
         [0004]     Central vacuum systems where a vacuum hose can be reeled between extended and retracted positions are known. An example of such a hose driving system in a wall mounted central vacuum system is found in U.S. Pat. No. 5,740,581 to Harrelson, II. A problem with a driven hose in a vacuum system is that normal movement of the hose between extended and retracted positions can occasionally be obstructed, where the hose gets jammed. Continued driving of the hose in such conditions risks damaging the hose. There is a need to detect when a jam condition occurs so that the driving mechanism can be terminated. It is known to measure the torque on an electric motor that drives a vacuum hose, and stop the motor when torque exceeds a predetermined value, assuming that increased torque means that a jam condition has occurred. See, for example, the Harrelson, II &#39;581 patent.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is embodied in a vacuum system comprising a cabinet adapted to be mounted to a wall. The vacuum system includes a hose connectable to a vacuum source and extendable from the cabinet between a retracted position where most of the hose is within the cabinet and an extended position where most of the hose is out of the cabinet. A rotatable shaft drives the hose between the retracted and extended positions, and a power source causes the rotatable shaft to rotate. A sensor is provided to measure the speed of the shaft as it rotates. The power source is disengaged from the rotatable shaft when the speed drops below a predetermined threshold while the hose is being extended or retracted and not at the retracted or extended positions.  
         [0006]     Typically, the power source will be a motor. Preferably, the motor is reversible. The preferred sensor is a Hall effect sensor.  
         [0007]     A hose storage compartment can be provided in the cabinet where the hose is stored when the hose is in the retracted position. Also, a retraction stop mechanism can be provided to limit retraction of the hose. In addition, or alternatively, an extension stop mechanism can limit extension of the hose.  
         [0008]     Preferably, the retraction stop mechanism comprises a sleeve mounted to the hose and a limit switch mounted to the cabinet so that the sleeve will activate the limit switch to halt retraction of the hose. Similarly, the extension stop mechanism comprises a projection on the hose and a limit switch mounted to the cabinet so that the projection will activate the limit switch to halt extension of the hose.  
         [0009]     In one aspect of the invention, a handle is mounted to the hose and is retained out of the cabinet when the hose is in the retracted position. The handle has a light, preferably, an LED. The handle can have a nozzle portion and a grip portion, with the nozzle portion angled relative to the grip portion. Ideally, the handle nests within a collar on a top wall of the cabinet, canted relative to the cabinet for ease of access.  
         [0010]     In another aspect of the invention, a portable vacuum unit is detachably mountable to the cabinet and has a tank and an inlet port in fluid communication with the tank. The hose is connectable to the inlet port and the vacuum source is located in the portable vacuum unit to draw air from the inlet port into the tank. A portable vacuum hose can be mounted to the portable vacuum unit for use when vacuuming with the portable vacuum unit. Preferably, the portable vacuum unit has an outlet port, configured to receive a blower hose to direct air from the outlet port as a blower.  
         [0011]     In a further aspect of the invention, the hose and the inlet port are automatically connected when the portable vacuum unit is docked to the cabinet. The cabinet has a power outlet and the portable vacuum unit receives power from the power outlet when it is docked with the cabinet. The portable vacuum unit has a power switch operable to actuate the vacuum source when the portable vacuum unit is detached from the cabinet, and a bypass mechanism to bypass the power switch when the portable vacuum unit is docked with the cabinet. Preferably, the vacuum source and the power outlet are automatically connected when the portable vacuum unit is docked with the cabinet.  
         [0012]     In yet another aspect of the invention, the motor is operable in response to actuation of switches on the hose, and the switches can be in the handle. Preferably, the switches actuate the motor by wireless signals. In this embodiment, the hose has a transmitter and the cabinet has a controller with a receiver, the controller being electrically connected to the motor, so that signals from the switches are transmitted to the receiver for actuation of the motor by way of the controller. Further, the vacuum system can have a clutch mechanism to release the hose so that it can move independently of the power source. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     In the drawings:  
         [0014]      FIG. 1  is a perspective view of a vacuum system according to the invention mounted on a wall.  
         [0015]      FIG. 2  is a perspective view of the vacuum system of  FIG. 1  with the lower portion door open.  
         [0016]      FIG. 3  is a perspective view of the vacuum system of  FIGS. 1 and 2  with the upper portion panel shown in phantom.  
         [0017]      FIG. 4  is a perspective view of the portable vacuum unit of the vacuum system of  FIG. 1 .  
         [0018]      FIG. 5  is a perspective view of the portable vacuum unit of  FIG. 4  mounted on a wall.  
         [0019]      FIG. 6  is an exploded view of the portable vacuum unit of  FIG. 4 .  
         [0020]      FIG. 7  is a cross-sectional view of the portable vacuum unit taken long line  7 - 7  of  FIG. 4 .  
         [0021]      FIG. 8  is an exploded view of the gearbox in the hose drive assembly according to the invention.  
         [0022]      FIG. 9  is a partial cross-sectional view of the hose drive assembly showing the extension limit mechanism and a first embodiment of a retraction limit mechanism.  
         [0023]      FIG. 10  as a partial cross-sectional view of the hose drive assembly showing the extension limit mechanism and a second embodiment of a retraction limit mechanism.  
         [0024]      FIG. 11  is a perspective view of the handle.  
         [0025]      FIG. 12  is a schematic diagram showing the interaction of various components of the vacuum system according to the invention.  
         [0026]      FIG. 13  is a schematic diagram of a bypass circuit for delivering power to the portable vacuum unit.  
         [0027]      FIG. 14  is a cross-sectional view of a bypass mechanism for actuating the bypass circuit of  FIG. 13 .  
         [0028]      FIG. 15  is a schematic diagram of an alternative bypass circuit for delivering power to the portable vacuum unit.  
         [0029]      FIG. 16  is a cross-sectional view of a bypass mechanism for actuating the bypass circuit of  FIG. 15 .  
         [0030]      FIG. 17  is a side view, partly in cross-section, of an alternative hose connection between the portable vacuum unit and the cabinet.  
         [0031]      FIG. 18A  is a partial plan view of the gearbox showing a clutch mechanism and the engaged position according to the invention.  
         [0032]      FIG. 18B  is a partial plan view of the gearbox showing a clutch mechanism of  FIG. 18A  in the disengaged position.  
         [0033]      FIG. 18C  is a plan view of the control plate for the clutch mechanism of  FIGS. 18A and 18B . 
     
    
     DETAILED DESCRIPTION  
       [0034]     The invention is embodied in a vacuum system  10  illustrated generally in  FIGS. 1-3 . The vacuum system  10  comprises a cabinet  12  adapted to be mounted on a wall. Here, the cabinet  12  is mounted on a slot wall construction of the type sold by Whirlpool Corporation under the Gladiator® trademark and disclosed in U.S. Pat. No. 6,811,043. The cabinet  12  comprises an upper portion  14  and a lower portion  16 , both bounded by a rear wall  18  and opposed sidewalls  20 ,  22 . The upper portion  14  houses a hose storage compartment  24  covered by a removable panel  26  which can provide access to the compartment.  
         [0035]     Inside the storage compartment  24  is a considerable length of vacuum hose  28 , preferably on the order of 40 feet in length. The vacuum hose  28  is typically corrugated or formed with a spiral rib, and may be extendable and compressible. The upper end of the vacuum hose  28  extends through a hose drive assembly  30  to a handle  32 . The handle  32  nests within a collar  34  around an opening  35  in an upper wall  36  of the cabinet  12  with the vacuum hose  28  and/or handle  32  extending through the opening  35 . The handle  32  is preferably canted relative to the cabinet when stored as shown. The lower end of the vacuum hose  28  fluidly communicates with a conduit  38  that projects into the lower portion  16  through a wall  40  that separates the lower portion  16  from the upper portion  14 . A female coupler  39  can be provided on the end of the conduit  38 .  
         [0036]     The lower portion  16  has a door  42  that provides access to a lower compartment  44 . The lower compartment  44  is also open at a lower end of the cabinet  12 . A portable vacuum unit  46  is removably mountable to the cabinet  12  within the lower compartment  44 . In this embodiment, a ledge  48  is mounted to each sidewall  20 ,  22  within the lower compartment  44 . The portable vacuum unit  46  rests on the ledges  48  so that a portion of it is housed within the lower compartment, accessible by way of the door  42 , and another portion of it extends through the open lower end of the cabinet  12 . The cabinet  12  could just as easily be sized such that the portable vacuum unit is completely received within the interior of the cabinet.  
         [0037]     The lower compartment  44  also houses one or more enclosures  50 ,  52  for supporting electrical circuitry and controllers that operate the hose drive assembly  30  and the portable vacuum unit  46  when it is mounted within the cabinet  12 . In addition, the lower compartment  44  can also house additional vacuum attachments such as extension  54 .  
         [0038]     Preferably, the cabinet  12  will be mounted to a wall in a position so that the portable vacuum unit  46  will be more than 1½ to 2 feet off the floor. This is especially important in a garage where flammable vapors may accumulate closer to the floor. On the other hand, the cabinet  12  should not be mounted so high that the handle  32  is difficult to access. In this respect, it is within the scope of the invention for the handle  32  and the vacuum hose  28  to extend from the cabinet  12  at some point other than the top of the cabinet.  
         [0039]     Turning now to  FIGS. 4-7 , the portable vacuum unit  46  is more clearly illustrated. The portable vacuum unit  46  comprises a platform  56  that supports a motor housing  58  above it and suspends a tank  60  beneath it. The tank  60  is removably mounted to the platform  56  by clips  62  or other conventional fasteners. The tank  60  will also preferably have feet  64  that will enable the portable vacuum unit  46  to rest stably on a horizontal surface. Preferably, the portable vacuum unit  46  will have some means to enable it to be hung separately on a wall  47  as shown in  FIG. 5 . Such means can include hooks or mating fasteners such utilized with the Gladiator® system, or something as simple as one or more receptacles to be received on corresponding wall-mounted hooks.  
         [0040]     It will be appreciated that the portable vacuum unit  46  can function as a wet/dry vacuum, and therefore the tank  60  will have a drain  66  disposed at a lower portion thereof. The drain  66  will be sealed by a removable cap  68 .  
         [0041]     Referring primarily to  FIGS. 6 and 7 , the platform  56  has a centrally disposed outlet opening  70  and, to one side thereof, an upwardly extending cone  72 . The upper end of the cone  72  defines an inlet opening  74 . An impeller housing  76  is disposed over the outlet opening  70  and defines an exhaust channel  78  to an outlet opening  80  opposite the inlet opening  74 . A vacuum motor  82  is positioned to drive an impeller within the impeller housing  76  in conventional manner. The motor housing  58  houses the inlet opening  74 , the outlet opening  80 , the impeller housing  76 , and the vacuum motor  82 .  
         [0042]     A handle  84  extends upwardly from the motor housing  58 , and may be formed of two clamshell halves  86 ,  88 , and a bridge  90 . One side of the handle  84  defines a vacuum port  92  and the other side of the handle defines a blower port  94 . A vacuum conduit  96  extends from the vacuum port  92  to the inlet opening  74 , and an exhaust conduit  98  extends from the outlet opening  80  to the blower port  94 . A male adapter  100  extends out of the vacuum port  92  in fluid communication with the vacuum conduit  96 . A power switch  102  is mounted in the handle  84  and is electrically connected to the vacuum motor  82 . A conventional electrical cord  104  with plug  105  is also wired in conventional manner to the switch  102  and to the vacuum motor  82  to deliver power.  
         [0043]     A cylindrical filter  106  depends from the platform  56  coaxially around the central outlet opening  70 . Preferably, a longitudinally slotted support cup  108  is secured to the platform  56  around the central outlet opening  70 . A leg assembly  110  comprising a central securing plate  112  and four radially extending legs  114  is secured to the support, cup  108  by a threaded bolt  116 . The cylindrical filter  106  is securely retained between securing plate  112  and the bottom of the platform  56 . It will be appreciated that the leg assembly  110  enables the platform  56 , motor housing  58 , handle  84 , and all the components enclosed therein to stand upright on the leg assembly when the tank  60  is removed from the platform  56 .  
         [0044]     The motor housing  58  can further be adapted with various slots and cradles to support assorted tools and attachments  117  customarily used in vacuuming operations. For example, a separate onboard hose extension  118  rests in a cradle  120  around the handle  84 . It is also within the scope of the invention for the portable vacuum unit  46  to be cordless, i.e., having an onboard rechargeable battery that can, for example, the automatically recharged when the portable vacuum unit is docked in the cabinet  12 .  
         [0045]     Turning now to  FIGS. 8-10 , the hose drive assembly  30  is illustrated in greater detail. The hose drive assembly  30  comprises a gearbox  122 , preferably formed of two clamshell halves  123 ,  125  that define an upper wall  124  and the lower wall  126 . An aperture  128  in the upper wall  124  is located in registry with an aperture  130  in the lower wall  126 . The diameters of the apertures  128 ,  130  are such that the vacuum hose  28  can extend through the gearbox  122  and move freely through the apertures in both directions. The gearbox  122  houses a reversible drive motor  132  having a shaft and a worm (not shown in  FIG. 8-10 ). A drive spur gear  134  mounted to a shaft  136  engages the worm to rotate when the reversible drive motor  132  is actuated. A first roller spur gear  138  is mounted to a shaft  140  and engages the drive spur gear  134 . A first roller  142  is disposed to move with the first roller spur gear  138 , preferably by either mounting to the first roller spur gear  138  or mounting to the shaft  140 . A second roller spur gear  144  is mounted to a shaft  146  and engages the first roller spur gear  138 . A second roller  148  is disposed to move with the second roller spur gear  144 , preferably by either mounting to the second roller spur gear  144  or mounting to the shaft  146 . The first and second rollers  142 ,  148  have recessed sheaves  150  that define a gap  152  between the rollers. The vacuum hose  28  extends between the apertures  128 ,  130  through the gap  152  so that the corrugations or ribs on the hose engage the sheaves  150  of the first and second rollers  142 ,  148 .  
         [0046]     It will be apparent that when the reversible drive motor  132  is actuated in an extending direction, the worm causes the drive spur gear  134  to rotate in the direction shown by the arrow A in  FIG. 8 . Similarly, rotation of the drive spur gear  134  causes the first roller spur gear  138  and the first roller  142  to rotate in the opposite direction shown by the arrow B in  FIG. 8 . In addition, rotation of the first roller spur gear  148  causes the second spur gear  144  and the second roller  148  to rotate in the same direction as the drive spur gear  134 , shown by the arrow A. As the two rollers  142 ,  148  rotate in the indicated directions, the sheaves  150  bear against the corrugations or ribs to urge the vacuum hose  28  through the gap  152 , through the opening  35  in the cabinet  12 , and out of the hose storage compartment  24 . Conversely, if the reversible drive motor  132  were to be actuated in a retracting direction opposite the extending direction, the two rollers  142 ,  148  will be urged to rotate in opposite directions from that indicated in  FIG. 8 , thereby urging the vacuum hose  28  into the storage compartment  24 .  
         [0047]     The hose drive assembly  30  further comprises a retraction stop mechanism  154  to stop the reversible drive motor  132  when the vacuum hose  28  reaches a predetermined retraction limit, preferably with the vacuum hose completely within the storage compartment  24 , and the handle  32  nested within the collar  34 . It also comprises an extension stop mechanism  156  to stop the reversible drive motor  132  when the vacuum hose  28  reaches a predetermined extension limit.  
         [0048]     Exemplary embodiments of a retraction stop mechanism  154  and an extension stop mechanism  156  are illustrated in  FIGS. 9 and 10 . Looking at  FIG. 9 , a first embodiment of an retraction stop mechanism  154  includes a hose conduit  158  extending upwardly from the upper aperture in the gearbox  122 , and terminates in an annular slot  160  at or beneath the collar  34 . A limit switch  162 , preferably in the form of a microswitch, is mounted within the storage compartment  24  adjacent the annular slot  160 . A trigger  164  is mounted within the annular slot  160  and movable between a first position where it engages the limit switch  162  and a second position where it does not engage the limit switch. The trigger  164  is preferably biased to the second position. The upper end of the vacuum hose  28  near the handle  32  carries an annular sleeve  166  sized to be received within the annular slot  160 . When the annular sleeve  166  is nested within the annular slot  160 , it urges the trigger  164  to the first position where it engages the limit switch  162 . The limit switch  162  is electrically connected to the reversible drive motor  132 , preferably by way of a printed circuit board (PCB) that controls the drive motor operation in a manner that when the limit switch is engaged by the trigger  164  being in the first position, the reversible drive motor  132  is deactivated. In operation, as the vacuum hose  28  approaches its limit of retraction, the annular sleeve  166  is received within the annular slot  160  where it contacts the trigger  164 , urging the trigger to the first position where it engages the limit switch  162  to deactivate the reversible drive motor  132 .  
         [0049]     Looking now at  FIG. 10 , a second embodiment of a retraction stop mechanism  154 ′ includes a hose conduit  158  extending upwardly from the upper aperture  128  in the gearbox  122 . The hose conduit  158  terminates in an annular cup  170 . A limit switch  172 , preferably in a form of a microswitch, is mounted within the annular cup  170 . A compression spring  174  extends upwardly from the bottom of the annular cup  170  and surrounds but does not engage the vacuum hose  28 . A sleeve  176  is secured to the upper end of the compression spring  174 , and has an open socket  178  at an upper end thereof. A nub  180  depends from the sleeve  176  outside the compression spring  174  in line to engage the limit switch  172  when the compression spring  174  is compressed, but not engage the limit switch  172  when the compression spring  174  is uncompressed. The open socket  178  is sized to contact the lower end of the handle  32 , yet to allow the vacuum hose  28  to move freely through it. In operation, as the vacuum hose  28  approaches its retraction limit, the lower end of the handle  32  contacts the open socket  178 , and bears against the sleeve  176  causing it to compress the compression spring  174 . As the spring  174  compresses, the nub  180  is urged into contact with the limit switch  172 , deactivating the reversible drive motor  132 .  
         [0050]     The extension stop mechanism  156  includes an open cup  182  depending from the lower aperture  130  of the gearbox  122 . A limit switch  184 , preferably in the form of a microswitch, is mounted within the storage compartment  24  adjacent the open cup  182 . A trigger  186  is mounted within the open cup  182  and movable between a first position where it engages the limit switch  184  and a second position where it does not engage the limit switch. The trigger  186  is preferably biased to the second position. A projection  188 , preferably in the form of the spherical mounting on the exterior of the vacuum hose  28  is sized to enter the open cup  182  and move the trigger  186  to the first position as the vacuum hose  28  approaches its maximum extension, thereby engaging the limit switch  184 . The limit switch  184  is electrically connected to the reversible drive motor  132 , preferably by way of the PCB in a manner that when it is engaged, the reversible drive motor  132  is deactivated. Moreover, the size of the projection  188  is such that further extension of the vacuum hose  28  is prohibited by the contact the projection  188  with the open cup  182  or the lower aperture  130  of the gearbox  122 .  
         [0051]     It is within the scope of the invention for the retraction stop mechanism  154  or the extension stop mechanism  156 , or both, to be utilized with a hose drive assembly  30  in any vacuum system, whether or not incorporated in the present embodiment. For example, they can be used in portable vacuum systems, wall-mounted vacuum systems, and central vacuum systems.  
         [0052]     Looking now  FIG. 11 , the handle  32  comprises a grip portion  180 , and a nozzle portion  182 . The nozzle portion  182  preferably extends an obtuse angle relative to the longitudinal axis of the grip portion  180 . The nozzle portion  182  is also sized to frictionally receive one or more vacuum attachments  54 ,  117  either stored in the lower compartment or cradled in the portable vacuum unit  46 .  
         [0053]     It is contemplated that control of the vacuum motor  82  and control of the hose drive assembly  30  will be wireless from the handle  32 . Thus, a transmitter enclosed in the handle  32  will transmit signals from an “on” switch to turn on the vacuum motor  82 , and an “off” switch to turn off the vacuum motor  82 , a “forward” switch to actuate the reversible drive motor  132  in the extending direction, and a “reverse” switch to actuate the reversible drive motor  132  in a retracting direction. There may also be an “off” switch to turn off the reversible drive motor  132  between the extension and retraction limits. In the present embodiment of the handle  32  illustrated in  FIG. 11 , the “on” switch and “off” switch for the vacuum motor  82  are encompassed in a single toggle key  185 , the forward switch is actuated by a forward key  187 , and the reverse switch is actuated by a reverse key  189 . The “off” switch for the reversible drive motor  132  can be either a separate key, or preferably toggled from either the forward key  187  or the reverse key  189 . Preferably, the RF frequency for transmission is 433 MHz, and the modulation method is ASK.  
         [0054]     The handle  32  also has a light  191 , preferably an LED, which activates whenever the “on” switch is activated. The light  191  is preferably directed in same direction as the nozzle  182  to provide illumination to the area to be vacuumed by the nozzle. It is within the scope of the invention for the handle light  191  to be utilized in any vacuum system, whether or not incorporated in the present embodiment. For example, it can be used in portable vacuum systems, wall-mounted vacuum systems, and central vacuum systems.  
         [0055]     Looking now also at  FIG. 12 , the electronic interaction among the various components is illustrated schematically. The cabinet  12  houses the gearbox  122 , which includes the reversible drive motor  132 . A receiver  190  is located in the cabinet  12 , preferably in the enclosure  52 . Also, a controller  194 , preferably disposed in the enclosure  52  of the lower compartment  44 , includes a processor  192 . The controller  194  is electrically connected on the one hand to the gearbox  122  (preferably to the PCB connected to the reversible drive motor  132 ), and on the other hand to a power socket  196  also disposed in the enclosure  52 . The handle  32  is connected to the cabinet  12  by way of the vacuum hose  28 , but electrically, a wireless connection is preferred. The portable vacuum unit  46 , as explained above, is a separate device. A user wishing to use the portable vacuum unit  46  apart from the cabinet  12  need only plug the electrical cord  104  into a conventional power socket using the plug  105 , and turn on the power switch  102 .  
         [0056]     In this embodiment in order to use the portable vacuum unit  46  with the vacuum hose  28  of the cabinet  12 , the user must do three things, manually, once the portable vacuum unit is installed in the cabinet: (1) connect the conduit  38  to the vacuum port  92 , (2) plug the electrical cord  104  into the power socket  196 , and (3) turn on the power switch  102 . It will be understood that when the portable vacuum unit  146  is so docked, no power is delivered to the power socket  196 ; the portable vacuum unit is placed only in a condition of readiness for operation.  
         [0057]     All control of the vacuum system  10  can thereafter be accomplished entirely from the handle  32 . Pressing the toggle key  185  to actuate the “on” switch sends a coded signal to the receiver  190 , whereupon the processor  192  decodes the signal and energizes the power socket  196 . Conversely, pressing the toggle key  185  to actuate the “off” switch sends a coded signal to the receiver  190 , whereupon the processor  192  decodes the signal and de-energizes the power socket  196 . Similarly, pressing the forward key  187  sends a coded signal to the receiver  190 , whereupon the processor  192  decodes the signal and turns on the reversible drive motor  132  in the extending direction. The vacuum hose  28  will be automatically extended from the hose storage compartment  24  during actuation of the hose drive assembly  30 , and the user can guide the extension of the hose with the help of the handle  32  to the fully extended position, whereupon the hose drive assembly  30  will be shut off by the extension stop mechanism  156 . If the user wanted the vacuum hose  28  to be partially extended, pressing the forward key  187  again will stop the hose drive assembly  30 . By continually pressing the forward key  187  or the reverse key  189 , as needed, the user can position the vacuum hose  28  is desired.  
         [0058]     It is within the scope of the invention for the forward key  187  and the reverse key  189  to provide continuous activation of the hose drive assembly  30 . In other words, as long as the forward key  186  is pressed between the extension and retraction limits, the reversible drive motor  132  will be energized in the extension direction. When the forward key  187  is released, the reversible drive motor  132  will be shut off. Similarly, as long as the reverse key  189  is pressed between the extension and retraction limits, the reversible drive motor  132  will be energized in the retraction direction. When the reverse key  189  is released, the reversible drive motor  132  will be shut off. In any event, it is contemplated that when the vacuum hose  28  is fully retracted and the limit switch  162  or  172  is actuated, the reverse key  189  will be inoperative so as to prevent damage to the hose. Similarly when the vacuum hose  28  is fully extended and the limit switch  184  is actuated, the forward key  187  will be inoperative so as to prevent damage to the hose. In order to stabilize operation of the reversible drive motor  132 , a step start of the motor is initiated preferably within the first second of actuation.  
         [0059]     To prevent damage to the vacuum hose  28  and to the hose drive assembly  30  in the event the vacuum hose  28  becomes jammed during extension or retraction, an anti-jamming circuit  198  is provided. In the anti-jamming circuit  198 , a Hall effect sensor  200  is disposed in the gearbox  122  near a magnetic ring on the shaft of the reversible drive motor  132 . The Hall effect sensor  200  monitors the speed of the reversible drive motor  132  and sends a signal indicative of the speed to the processor  192 . The processor  192  is programmed to recognize a lower limit of normal speeds for the reversible drive motor  132 , say 3000 rpm. It is assumed that if the motor speed drops below 3000 rpm when neither an “off” switch nor a limit switch is activated, there is a jammed condition, and the controller  194  will turn off the reversible drive motor  132 . Preferably, the controller  194  will permit the system to reset to an operative condition only when the jamming problem is resolved.  
         [0060]     Any one or all of the three manual operations for connecting the portable vacuum unit  46  to the cabinet  12  can be automated. For example, a mechanism can be provided to automatically bypass the power switch  102  when the portable vacuum unit  46  is mounted to the cabinet  12 , thereby obviating the need to turn on the power switch. Two variations of such a mechanism are illustrated in  FIGS. 13-16 . In the first variation shown in  FIGS. 13 and 14 , a protrusion  202  extends from the rear wall  18  of the cabinet  12 . Some portion of the portable vacuum unit  46 , preferably the motor housing  58  has an aperture  204  sized to receive the protrusion  202 . A switch module  206  is disposed immediately behind the aperture  204  and comprises a button  208  movably connected to a wall  210 . A reed switch  212  is mounted adjacent to the path of movement of the button  208 . The button  208  carries a magnet  214 , and is biased to a position where the magnet  214  is not adjacent the reed switch  212 , yet is positioned to contact the protrusion  202  when the protrusion is received in the aperture  204 .  
         [0061]     As the portable vacuum unit  46  is mounted in the cabinet  12 , as for example by resting on the ledges  48  as explained above, the motor housing  58  is brought near the rear wall  18  of the cabinet  12 . The aperture  204  is located such that it goes over the protrusion  202 . Simultaneously as the protrusion  202  extends through the aperture  204 , it bears against the button  208 , and urges the button to move against its bias toward the wall  210 . As the button  208  moves, the magnet  214  passes the reed switch  212 , activating it. Actuation of the reed switch  212  energizes a coil  216  that, in turn, triggers a relay  218  to close a circuit between the electrical cord  104  and the vacuum motor  82 . Thus, upon placement of the portable vacuum unit  46  within the cabinet  12 , the user need not perform the manual operation of turning the power switch  102  on because the power switch is effectively automatically bypassed by triggering the relay  218 .  
         [0062]     An alternative to the aforementioned bypass circuit is shown in  FIGS. 15-16  where like components bear like reference numerals. The difference in this circuit is that instead of using the more complex magnetically operated reed switch with coil and relay, a simple microswitch  220  is mechanically actuated by the button  208 .  
         [0063]     Another manual operation the can be automated is connecting the conduit  38  to the vacuum port  92 . An example of a structure to accomplish this operation is shown in  FIG. 17 . The conduit  38  extending from the vacuum hose  28  into the lower compartment  44  has an extension  220  projecting outwardly from the rear wall  18 . A female coupler  222  is located on the end. The portable vacuum unit  46  has a conduit  224  extending rearwardly from the vacuum port  92  on the end of which is a male coupler  226 . The couplers  222 ,  226  slidably mate, and one or both has a flexible sealing gasket to seal the connection, at least when a vacuum is drawn through the conduits  220 ,  224 . Thus, as the portable vacuum unit  46  is placed within the cabinet  12 , as for example to rest on the ledges  48 , the male coupler  226  is simultaneously received within the female coupler  222  to automatically connect the conduit  38  to the vacuum port  92 .  
         [0064]     It is further contemplated that an automatic power connection can be obtained upon docking the portable vacuum unit  46  to the cabinet  12  in at least a couple ways. In one alternative, the electrical cord  104  can be mounted on a spring-biased reel in the portable vacuum unit  46 . When fully reeled in, only the plug  105  projects from the portable vacuum unit  46 . The power socket  196  can be disposed within the lower compartment  44  so that as the portable vacuum unit  46  is docked (for example, to rest on the ledges  48 ), the plug  105  is simultaneously urged into the socket  196 . In another alternative, a separate electrical coupling can be provided between the portable vacuum unit  46  and the cabinet  12 , with a bypass circuit in the portable vacuum unit to bypass the electrical cord  104  for delivery of power to the vacuum motor  92 .  
         [0065]     It has been found desirable to provide a clutch mechanism to disengage the vacuum hose  28  from the reversible drive motor  132  so that it can be manually extended or retracted, for example in the event of the power failure. An embodiment of such a clutch mechanism is illustrated in FIGS.  18 A-C.  FIGS. 18A and 18  B illustrate the three shafts  136 ,  140 , and  146  on which the spur gears  134 ,  138 , and  144  are respectively mounted. The vacuum hose  28  is shown in its relative position. The drive spur gear  134  has a clutch mechanism  250  interposed between it and the worm  252  on the shaft of the reversible drive motor  132 . The worm  252  engages a worm gear  254  mounted on the shaft  136  and spaced from the drive spur gear  134 . One of the worm gear  254  and the drive spur gear  134  rotates freely on the shaft  136 ; the other is fixed and rotates with the shaft  136 . A generally cylindrical coupler  256  is slidably mounted on the shaft  136  between the worm gear  254  and the drive spur gear  134 . The coupler  256  has an intermediate radial flange  258 , with a spur keyway  260  on the cylindrical wall facing the drive spur gear  134 , and a worm keyway  262  on the cylindrical wall facing the worm gear  254 . A worm key  264  extends from the shaft  136  and into the worm keyway  262 . A spur key  266  extends from a collar  268  on the drive spur gear  134 , and is sized to be received within the spur keyway  260 . The coupler  256  is biased by a compression spring  270  (between the worm gear  254  and the radial flange  258 ) so that the spur key  266  is received by the spur keyway  260 , as shown in  FIG. 18A . When the coupler  256  is so positioned, the drive spur gear  134  rotates with the worm gear  254 .  
         [0066]     A lever  272  is pivotally mounted to the gear box  122  so that one arm bears against the radial flange  258  and the other arm (either directly or by linkage) projects through a control plate  274  (see  FIG. 18C ). The control plate  274  has an L-shaped slot  276  where the lever  272  can be moved between an engaged position  278  and a disengaged position  280 . The “L” portion of the slot  276  can provide for a hold position  282  where the lever can be retained in a disengaged position.  
         [0067]     Looking now at  FIG. 18A , it can be seen that when the lever  272  is in the engaged position  278 , the coupler  256  is biased so that the spur key  266  is received in the spur keyway  260 , thus engaging the vacuum hose  28  with the reversible drive motor  132 . Looking now at fig year  18 B, it can be seen that when the lever  272  is in a disengaged position  280 , the arm bears against the radial flange  258  to urge the coupler  256  away from the drive spur gear  134  so that the spur key  266  is out of the spur keyway  260 . In this position, the drive spur gear  134  is free to rotate relative to the worm gear  254 , and consequently free to rotate relative to the reversible drive motor  132 . Thus, the vacuum hose  28  is disengaged from the reversible drive motor  132  and free to be manually retracted or extended as desired. In the hold position  282 , the lever  272  is retained in a disengaged position against the bias of the compression spring  270 .  
         [0068]     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.