Abstract:
A vacuum cleaner having a thermal cutoff assembly. The assembly includes a temperature sensor disposed proximate to a motor of the vacuum cleaner. When the temperature sensor reaches a predetermined temperature, a switching element in the assembly disconnects power shutting off the vacuum cleaner. The vacuum cleaner cannot be restarted until its power source has been manually disconnected and reconnected.

Description:
FIELD OF THE INVENTION  
         [0001]    This application claims the benefit of U.S. Provisional Application No. 60/035,357, filed Jan. 10, 1997.  
           [0002]    The present invention relates to a self-propelled upright vacuum cleaner comprising a unique HEPA-rated air filtration system. The present invention also relates to a self-propelled upright vacuum cleaner having a thermal cutoff circuit, a novel air routing configuration within the unit, and numerous other improvements and features.  
           [0003]    There is an increasing emphasis upon the cleanliness of air discharged from vacuum cleaners. Prior artisans have attempted to provide secondary filters for vacuum cleaner exhaust air streams. Although satisfactory in most respects, most known secondary filtering configurations are difficult to design and incorporate within the vacuum cleaner, thereby increasing the complexity, manufacturing time, and-cost of the unit. Furthermore, for assemblies employing replaceable filter elements, there is often considerable difficulty in replacing the element, particularly if it is located within the vacuum cleaner. Accordingly, there is a need for a vacuum cleaner comprising a secondary filtering assembly that overcomes the problems of the prior art. It would be particularly desirable to provide a vacuum cleaner with an easily replaceable filter element in combination with a sealed air path so that all air exiting the vacuum cleaner unit traveled through the filter prior to exiting the vacuum cleaner.  
           [0004]    Air leaks from a vacuum cleaner unit, such as leakage of the exhaust stream around the motor housing into the environment, not only introduce particulates and contaminants into the outside environment and thus bypass any secondary filter if so provided, but also decrease the overall efficiency of the unit. Thus, there is a need for a vacuum cleaner providing an improved internal air routing configuration which prevents or at least significantly minimizes exhaust air leaks in and around the lower enclosure, and particularly around the motor housing.  
           [0005]    It is desirable to provide a sensor and electrical circuit to stop operation of the vacuum cleaner motor in the event that the temperature of the motor exceeds a, predetermined temperature. Heating of the motor typically results from a blocked or plugged filter, or from one or more objects interfering with the operation of the rotating brush or floor element. Prior artisans have incorporated temperature sensors and motor switching circuits in vacuum cleaners. However, as far as is known, none of the known sensors and switching circuits utilized in vacuum cleaners provide an automatic reset feature. That is, all known vacuum cleaners with on board temperature sensors may be started immediately after the sensor sufficiently cools. Although satisfactory in most respects, this configuration still enables electrical power to be applied to the motor. This may result in damage to the motor, in the event the motor is bound or otherwise locked. Accordingly, there is a need for an improved temperature sensing and motor interlock circuit whereby a reset operation is performed to ensure that electrical power is not inadvertently directed to a locked motor.  
           [0006]    Self-propelled vacuum cleaners are known. However, much of the design and engineering efforts directed to such units are focused upon the drive assembly and vacuuming function. There remains an opportunity to improve other aspects of self propelled vacuum cleaners such as their noise level, electrical safety considerations, life of components such as the motor bearings, connections for an accessory hose, and configuration of the operator handle.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention achieves all the foregoing objectives and provides in a first aspect, a vacuum cleaner comprising a housing and a base unit pivotally attached to each other, a motor and motor housing disposed within the base unit, a drive assembly also disposed within the base unit and selectively coupled to the motor, a nested wand releasably retained along the exterior of the housing, a lower air conduit extending between the base unit and a lower end of the wand, and an upper air conduit extending between an upper end of the wand and a suction chamber defined within the housing.  
           [0008]    In another aspect, the present invention provides a vacuum cleaner comprising a lower base unit, an upper pivotable enclosure for housing a filter bag, a motor disposed within the lower base unit, a power cord and associated electrical conductors defining an electrical power circuit to the motor, and a thermal cutoff assembly including a temperature sensor disposed proximate to the motor for measuring the temperature of the motor, the thermal cutoff assembly including a switching element in the electrical power circuit that opens upon the temperature sensor sensing a temperature greater than a predetermined temperature setpoint.  
           [0009]    In yet another embodiment, the present invention provides a vacuum cleaner comprising a lower base unit, an upper enclosure for retaining a filter bag, the upper enclosure defining a suction chamber, and exhaust chamber, and an exhaust opening providing access from the exterior of the upper enclosure to the exhaust chamber, a motor and fan assembly disposed within the upper enclosure and in airflow communication between the suction chamber and the exhaust chamber, and a detachable filter assembly that releasably engages the upper enclosure at or near the exhaust opening.  
           [0010]    In yet another aspect, the present invention provides a vacuum cleaner comprising a lower base enclosure, an upper enclosure having internal walls dividing the upper enclosure into a suction chamber, an exhaust chamber, and a motor chamber, a motor and fan assembly disposed in a shroud which resides in the motor chamber, an air intake duct extending between the suction chamber and the shroud. The air intake duct engages either or both the suction chamber and the shroud along an unsealed interface.  
           [0011]    According to a further aspect of this invention a motor and transmission module selectively powers a base drive wheel and at least the motor of the module is encased in a shroud. The shroud is connected by an exhaust passageway to the air flow path leading ultimately to the final filter. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a perspective view of a preferred embodiment vacuum cleaner in accordance with the present invention;  
         [0013]    [0013]FIG. 1A is an exploded view of the preferred embodiment vacuum cleaner illustrated in FIG. 1;  
         [0014]    [0014]FIG. 1B is a side elevational view of the preferred embodiment vacuum cleaner illustrated in FIG. 1;  
         [0015]    [0015]FIG. 2 is a partial exploded view of the preferred embodiment vacuum cleaner housing, illustrating in greater detail the direction of airflow within the housing;  
         [0016]    [0016]FIG. 2A is a detailed view of the assembled housing shown in FIG. 2 having a bag cover removed;  
         [0017]    [0017]FIG. 2B is another view of the housing shown in FIG. 2 with the bag cover removed;  
         [0018]    [0018]FIG. 3 is a perspective view of the rear of the preferred embodiment vacuum cleaner;  
         [0019]    [0019]FIG. 4 is a detailed view illustrating the affixment of a preferred embodiment detachable filter to the rear housing of the preferred embodiment vacuum cleaner;  
         [0020]    [0020]FIG. 4A illustrates the filter shown in FIG. 4 attached to the rear housing and the direction of airflow from the preferred embodiment vacuum cleaner;  
         [0021]    [0021]FIG. 5 is a detail of the preferred embodiment filter used in the preferred embodiment vacuum cleaner;  
         [0022]    [0022]FIG. 6 is another view of the preferred embodiment filter;  
         [0023]    [0023]FIG. 7 is a schematic cross-sectional view of the preferred embodiment filter illustrating its orientation to the floor when the preferred embodiment vacuum cleaner is set to a fully reclined position;  
         [0024]    [0024]FIG. 8 is an exploded view of a suction motor and a motor shroud used in the preferred embodiment vacuum cleaner;  
         [0025]    [0025]FIG. 9 is a detailed view of the motor shroud shown in FIG. 8;  
         [0026]    [0026]FIG. 10. is another detailed view of the motor shroud shown in FIG. 8;  
         [0027]    [0027]FIG. 11 is a detailed view of the engagement between a hose adapter and the housing of the preferred embodiment vacuum cleaner;  
         [0028]    [0028]FIG. 11A is an elevational view of the adapter and housing assembly depicted in FIG. 11;  
         [0029]    [0029]FIG. 12 is a fragmentary view of the vacuum cleaner base illustrating the drive module and air flow therethrough; and  
         [0030]    [0030]FIG. 13 is a partially cross-sectional view of the handle assembly. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Referring to FIGS. 1, 1A,  1 B and  3 , a preferred embodiment vacuum cleaner  10  in accordance with the present invention is illustrated. The vacuum cleaner  10  comprises a rear housing  20 , an upper front cover  30 , a bag cover  80 , and a lower motor cover  50  that generally form the body of the vacuum cleaner  10 . The lower portion of the preferred embodiment vacuum cleaner  10  comprises an upper base  40  having a front guard  120  and a plurality of wheels including rear wheels  110 . The upper portion of the preferred embodiment vacuum cleaner  10  further comprises a handle  90 , a grip  100 , and a side mounted tool caddie insert  34 . Disposed along the rear of the vacuum cleaner  10  is a final filter  60 .  
         [0032]    Referring specifically to FIG. 1A, other components of the preferred embodiment vacuum  10  are as follows. The handle  90  is disposed between the front cover  30  and the upper portion of the rear housing  20 . The handle  90  preferably has an arcuate bend proximate to its upper distal end  91 . The bend is such that the distal end  91  is directed toward the rear of the vacuum cleaner  10 . The grip  100  is affixed to a handle cover  102  and this assembly is slidably mounted on the upper distal end  91  of the handle  90 . Various switches and controls may also be provided proximate to the distal end  91  of the handle  90  such as, but not limited to, a neutral lock mechanism  130  and related selector springs  132  and a selector spacer  134 . In addition, one or more switches may be located at the distal end  91  of the handle  90  for controlling the operation of the vacuum cleaner  10 . Other controls such as an on/off switch  140  and various potentiometer type controls such as a slide control  142  are preferably disposed and affixed to the front cover  30 .  
         [0033]    The upper base  40  and a lower base  180  engage each other and generally form a lower enclosure that houses the drive motor and brush assembly as follows. A drive motor  230  is disposed and retained within the enclosure formed by the upper base  40  and the lower base  180 . The drive motor  230  is operatively coupled to a transmission  240  that also resides within the enclosure formed by the upper and lower bases  40  and  180 . Rotatably secured to, or retained within, the lower base  180  are a plurality of wheels. A pair of rear wheels  110  are rotatably affixed to the lower base  180  by respective axles  111 . Disposed proximate the front of the lower base  180  is a wheel carriage  112  that rotatably supports a front axle  116  having a pair of front wheels  114  secured at its ends. Also disposed within the enclosure formed by the upper base  40  and the lower base  180  is a rotatable brush or disturbulator  170 . The disturbulator  170  is rotated by a disturbulator belt  172 . A belt cover  174  is utilized to cover the belt  172 .  
         [0034]    Referring further to FIG. 1A, preferably disposed proximate to the lower portion of the rear housing  20  are a suction motor  210  and a motor shroud  220 . The suction motor  210  draws air through the enclosure formed by the upper and lower bases  40  and  180 , i.e. in the vicinity of the disturbulator  170 , through a lower hose  72 , a nested wand  78 , an upper hose  70 , a bag filter  270  disposed within a bag chamber described below, a second filter  260 , an air intake duct  250 , through the motor shroud  220  and eventually into the final filter  60  as described in greater detail below. A single screw is utilized for engaging the lower hose  72  connector to the lower base  180 . A hose union  74  and other conventional coupling assemblies may be used to complete the airway. A unique releasably locking hose adapter  71 , described in greater detail below, is preferably utilized to couple the upper hose  70  to the bag chamber within the rear housing  20 .  
         [0035]    An electrical power cord  200  and one or more cord release members  202  are provided along the rear of the vacuum cleaner  10 . The power cord  200  provides electrical power to the suction motor  210  and the drive motor  230 . The preferred embodiment vacuum cleaner  10  also comprises a headlight  150  and a lens  152  disposed in or upon the motor cover  50 . A height adjustment assembly and knob  160  is provided for the lower base unit.  
         [0036]    The preferred embodiment vacuum cleaner also comprises a variety of cleaning tools or attachments. A side mounted tool caddie insert  34  is preferably utilized to releasably retain these tools such as for instance a crevice tool  190 , an upholstery nozzle  192 , and a brush  194 . An extension wand  76  is also provided. An attachment tool is utilized by detaching the hose  70  from the nested wand  78  at their coupling along the rear of the vacuum cleaner  10 , as best depicted in FIG. 3. Upon release of the hose  70  from the nested wand  78 , one of the previously noted tools  190 ,  192 , or  194 , or the extension wand  76  can be attached to the free end of the hose  70 .  
         [0037]    Referring to FIG. 1B, another aspect of the preferred embodiment vacuum cleaner  10  is the orientation of the upper housing and handle  90  to the base when the vacuum cleaner  10  is in its stationary upright position. This position is reached when the vacuum cleaner is placed in its accessory vacuuming mode. As evident in FIG. 1B, the upper housing is preferably oriented forward at some angle X from vertical. This orientation results in a more stable assembly than if the upper housing were oriented along a generally vertical axis. This becomes increasingly important as the bag filter  270  (shown in FIG. 1A) fills up with dirt and debris, thereby increasing in weight. It is most preferred that the angle X be about 8-½°. The present invention vacuum cleaners include other configurations in which the upper housing and handle are angled forward.  
         [0038]    Referring further to FIG. 1A, a conventional handle release  92  and a release spring  94  control the angular orientation of the upper portion of the vacuum cleaner housing and handle. The handle  90  and related attachments such as switches and grips, may be entirely detachable from the vacuum cleaner  10 , or designed to pivot so that the assembly may be folded downward toward the floor to a horizontal, or substantially horizontal, position. It is also contemplated that the handle could be mounted within the upper portion of the vacuum cleaner body in such a way that the handle becomes the movable portion or actuator utilized to control the operation of the vacuum cleaner. This would eliminate providing selector controls at the end of the handle  90  such as the selector  130 . In this contemplated embodiment, the linkage connection to the control cable, i.e. a sheathed transmission shifting cable described below, would occur within the top portion of the vacuum cleaner body or housing. In many or all of these embodiments, it is further contemplated that the handle  90  could be designed so that it could be readily removed from the main housing of the vacuum cleaner. This would significantly reduce the size of the shipping carton and reduce shipping costs. Other advantages would likely include quick customer assembly and reduction in the number of parts and parts costs. A reduction in the size of shipping carton and parts would further allow the packaged product to be more easily displayed in the sometimes, restricted shelf area found in many retail stores.  
         [0039]    It is also preferred to utilize a tilt switch, preferably disposed within the handle  90 , that prevents operation of the drive motor  230  depending upon the position of the handle. Preferably, the switch opens or closes an electrical control circuit depending upon the angular orientation of the handle. A switch comprising a ball bearing and raceway is disposed within the handle  90  and oriented such that when the handle is in an upright position, the ball bearing rolls or otherwise moves to a location along the raceway that results in an open electrical circuit between the switch terminals. The switch is also oriented so that when the handle is at any other position than its upright position, i.e. and so typically at some angle of inclination, the ball bearing rolls or moves to a location along the raceway that results in completion of the electrical pathway between the switch terminals. The tilt switch is preferably utilized in a control circuit governing operation of the drive motor  230  so that when the handle is in its upright position, the drive motor  230  will not operate. It is also contemplated that other types of switches utilizing other types of movable elements could be used. Furthermore, other types of interlocking switches could be used to prevent operation of the drive motor  230  when the handle  90 , is in its upright position. It is envisioned that electrical contacts could be provided between the tiltable body portion of the vacuum cleaner and the base portion. The electrically conductive contacts would contact one another only when the handle was tilted from its upright position. The contacts would be incorporated into an electrical control circuit governing operation of the drive motor  230 . Moreover, the location and placement of the switch could be elsewhere besides the handle, such as for instance, within the housing or base units of the vacuum cleaner.  
         [0040]    The various housing, cover, and base components described herein can be formed from a wide array of materials. A preferred material is molded polyurethane.  
         [0041]    The preferred embodiment vacuum cleaner  10  utilizes a unique and novel filtered airflow system as follows. Referring to FIG. 2, upon operation of the suction motor  210  generally disposed within the motor shroud  220 , air is drawn through the hose  70  and through the hose adapter  71  into the bag filter  270 . After passing through the walls of the bag filter  270 , shown as arrow A in FIG. 2, air enters a secondary filter  260  located at the inlet of the air intake duct  250 . Air passes through the air intake duct  250  shown as arrow B until it exits the duct  250  at the outlet shown as arrow C. The air then enters the inlet of the motor shroud  220 , shown as arrow D, and then is directed through the outlet of the motor shroud  220  shown as arrow E. The air is then directed to the final filter  60  as shown by arrow F. After passing through the final filter  60 , the air then exits the vacuum cleaner  10  through laterally oriented airflow openings along the side of the final filter  60  and described in greater detail below. The air exits as shown as arrows G.  
         [0042]    A bag chamber, i.e. an interior region that houses the bag filter  270 , is formed between the rear housing  20  and the bag cover  80 . During operation of the vacuum cleaner  10 , the bag chamber is usually at a negative pressure, i.e. a pressure less than atmospheric pressure.  
         [0043]    The preferred embodiment motor shroud  220  generally encloses the suction motor  210  and diverts all air through the final filter  60 . This configuration greatly simplifies gasket design and sealing issues otherwise encountered if a multi-component housing or shroud assembly was used. Although a one-piece sealed shroud enclosing the suction motor is preferred, the present invention includes additional embodiments including the use of a by-pass duct located either upstream, downstream, or on both ends of the suction motor. Other sealed enclosures are contemplated wherein the sealing is accomplished by conventional gaskets, adhesives or component welding.  
         [0044]    In a most preferred embodiment, air leaks are significantly reduced by recirculating airflow within the vacuum cleaner housing. Specifically, provisions are made to prevent exhaust air leaks from escaping to the environment before passing the air through the final filter  60 . This is accomplished by maintaining a negative pressure inside the vacuum cleaner housing, and particularly within the enclosure formed between the rear housing  20  and the bag cover  80 . This region of negative pressure may also extend in the vicinity behind the front cover  30 . Referring to FIGS. 2A and 2B, it is most preferred to use an ungasketed joint between the air duct  250  and a mounting shelf  252  provided in the rear housing  20 . The mounting shelf  252  defines an opening sized to accept and preferably support an end of the air duct  250 . The interface between the opening and the outer periphery of the air duct  250  is shown in FIGS. 2A and 2B as interface  251 . This interface is most preferably not sealed. As a result, exhaust leaks occurring in and around the upper portion of the air duct  250  are drawn into the bag chamber. Similarly, by providing an ungasketed joint between the lower region of the air intake duct  250  and the inlet of the motor shroud  220 , shown in FIG. 2B as joint  224 , potentional exhaust leaks in and around a gasketed joint between the lower portion of the air duct  250  and the suction motor  210  are drawn back into the motor shroud  220 . As can be seen, potential exhaust leaks from the positive pressure side of the air handling system are recaptured into the airstream instead of being exhausted to the environment before passing the airstream through the final filter  60 . This is achieved by maintaining a negative pressure inside the body or housing of the vacuum cleaner  10 . The negative pressure inside the body or housing is due to inherent and/or predetermined leaks between the various airflow handling components which allow air to enter the air intake duct  250  and the bag chamber.  
         [0045]    In another preferred embodiment, a flexible conduit shown in FIG. 2A as conduit  253  is provided between the motor bearings and the suction side or negative pressure side of the system. The conduit and resulting air flow through the conduit captures particles and contaminants otherwise leaking through the bearing or around the bearing and into the atmosphere. In the absence of such conduit, particles and contaminates leak from inside the enclosure or motor shroud to the outside environment. Another advantage of providing the flexible conduit  253  is that the resulting airflow therethrough draws air through and around the bearing thereby cooling the bearing and neighboring components. Preferably and with reference to FIGS. 2A and 8, the conduit  253  extends from a collar  590  disposed proximate a motor bearing. The conduit  253  extends to a location of lesser pressure, such as within the air duct  250 . Other installation sites for the end of the conduit  253  may be utilized instead of the air duct  250 . For instance instead of terminating the end of the conduit  253  at the air duct  250 , that end could be installed on the shelf  252  so that the conduit  253  is in communication with the region of the enclosure behind the filter wall  300 .  
         [0046]    The preferred embodiment vacuum cleaner  10  utilizes a HEPA-rated final filter  60  best shown in FIGS. 4, 4A,  5 ,  6 , and  7 . The HEPA filter captures at least 99.97% of particles having a diameter of about 0.3 microns. The rear housing  20  is particularly adapted for accommodating the final filter  60 . The rear housing  20  preferably comprises a rear wall  390  disposed between transversely extending first and second sidewalls  310  and  320 , respectively. A bottom arcuate wall  360  is provided that generally extends in the same direction as the sidewalls  310  and  320 . Defined generally within the center of the rear wall  390  is an opening  380  through which exiting air passes into the final filter  60 . The final filter  60  is detachably retained along the rear of the rear housing  20 . The final filter  60  is preferably supported by a support ledge  370 .  
         [0047]    The rear housing  20  further includes a filter wall  300  that partitions the interior of the vacuum cleaner  10 , i.e. the bag chamber, from the final filter  60 . Referring to FIG. 2A, the filter wall  300  segregates the filter  60 , disposed on the rear face of the rear housing  20 , from the bag chamber generally defined between the sidewalls  310 ,  320  and the shelf  252 . FIG. 2B is similar to FIG. 2A but illustrates the assembly with the filter wall  300  removed. Other structural aspects of the rear housing  20  are illustrated in FIGS. 2A and 2B. One or more support ribs  312  and  322  may be provided along either or both of the side walls  310  and  320 . One or more fastening bosses  330  are also provided for threadedly engaging fasteners or releasable clips that may be used for securing the motor cover  50 , the bag cover  80 , or the front cover  30  to the rear housing  20 .  
         [0048]    Specifically referring to FIGS. 5 and 6, the preferred embodiment final filter  60  generally comprises a filter outer cover plate  400  disposed between a plurality of transversely extending walls such as a first side wall  410 , a second side wall  420 , a top wall  430 , and a bottom wall  440 . A peripheral skirt  450  extends around the perimeter of the final filter  60  and provides a mounting lip or seat for sealing against the rear housing  20  when the final filter  60  is attached to the rear of the vacuum cleaner  10 . A plurality of airflow openings  460  are defined along the lateral regions of the final filter  60 . The final filter  60  may also comprise one or more bottom legs  470  that engage the rear housing  20  of the vacuum cleaner  10  when the final filter  60  is attached to the vacuum cleaner  10 . A retaining member  480  is preferably utilized to assist in releasably retaining the final filter  60  to the vacuum cleaner  10 . A filter element  490  such as a paper filter element, is disposed within the enclosure formed by the outer cover plate  400  and the walls  410 ,  420 ,  430 , and  440 .  
         [0049]    Referring to FIG. 7, during operation of the vacuum cleaner  10 , air exiting the rear housing  20  flows through the filter element  490  and out of the final filter  60 , i.e. through the airflow openings  460 , which direct the air laterally outward. The airflow openings  460  are defined along the sidewalls  410  and  420 . This is desirable, particularly when the vacuum cleaner  10  is in a fully reclined position such that its upper housing and handle are angled downward and near the floor  2 . The laterally oriented openings  460  direct the exiting air stream away from the floor  2 . The extent of reclining may be such that the handle is approximately horizontal. This orientation is useful so that the vacuum cleaner  10  has a low profile to thereby enable the vacuum cleaner to be used under furniture items and beds.  
         [0050]    The separate and detachable final filter  60  offers additional advantages. By using an external one-piece final filter assembly, there is no need for a separate housing or cover to house and protect the filter element. Furthermore, by utilizing a curved configuration for the outer cover plate  400  of the final filter  60 , exiting air is directed slightly upwards from the floor  2  when the vacuum cleaner is in a fully reclined position. This further minimizes debris on the carpet from being blown with the air. This is illustrated in FIG. 7. The rear cover plate  400  further acts as a shield to protect the paper filter element  490  and further deaden noise. In yet another embodiment, some of the various laterally disposed airflow openings  460  located along both sides of the final filter  60  can be eliminated and defined on only one side of the filter housing.  
         [0051]    Referring to FIGS. 8, 9, and  10 , the motor shroud  220  and suction motor  210  are illustrated in greater detail. The motor shroud  220  generally encloses the suction motor  210 . The motor shroud  220  is preferably cylindrical, comprising an arcuate wall  540  and an endwall  544 . The motor shroud  220  comprises a tangentially and outwardly extending air duct  530  defining a shroud opening  510  at its distal end  531 . The air duct  530  is in airflow communication with the final filter  60  disposed behind the filter wall  300  as shown in FIG. 2A. The air duct  530  may be attached to the mounting shelf  252 . Preferably provided proximate to the distal end  531  of the air duct  530  is a seal seat  532 . The seal seat  532  supports a pliable and flexible seal  520  that reduces air leaks between the mounting shelf  252  and the air duct  530  of the motor shroud  220 . One or more fasteners  570  and bosses  560  are used to affix and secure the assembly. A sealing and coupling ring  580  is preferably used between the suction motor  210  and the shroud  220 . The assembly of the motor  210 , the ring  580 , and the shroud  220  is preferably disposed within the lower portion of the rear housing  20 , and as best shown in FIG. 2A, against the second sidewall  320  of the rear housing  20 . Most preferably, the assembly is concentrically aligned with the pivot hub  350  defined in that sidewall. An alignment and support collar  590  is preferably utilized, as shown in FIG. 8 to facilitate support and engagement between the shroud  220  and the pivot hub  350  in the second sidewall  320 .  
         [0052]    The motor shroud  220  utilizes an interior isolation wall  500  as shown in FIG. 10. The isolation wall  500  generally blocks access to electrical components of the suction motor  210  and serves as a sound insulating barrier to decrease motor noise. Referring also to FIG. 9, the motor shroud  220  also provides one or more terminal apertures  550  that provide access to one or more electrical terminals  212  of the suction motor  210 . The preferred embodiment for forming a seal between the motor terminals  212  and the housing of the shroud  220  is by utilizing die cut or molded rubber or plastic members that create a seal within the motor terminal area. This prevents the motor exhaust air escaping through the shroud  220 . The present invention includes other embodiments for sealing the region between the motor terminals  212  and the shroud  220  such as, but not limited to, the following. A seal may be formed in this interface region by utilizing a liquid material such as a flowable adhesive, a hot melt adhesive, and silicone sealing materials as known in the art which fill the openings before curing to a hardened state. Alternatively, or in addition, a seal may be formed by utilizing a tight interference fit between the motor terminals  212  or their base, and openings within the motor shroud  220  such as the apertures  550 . Alternatively, or in addition, a seal may be formed by insert molding terminals or wires into the motor shroud  220  which can then be electrically connected to the motor terminals  212 . Furthermore, a seal may be formed by utilizing a tight interference fit between generally round holes in the motor shroud  220  and wires which connect to the motor terminals  212 . It is to be understood that any combination of the foregoing sealing techniques may be used.  
         [0053]    The preferred embodiment vacuum cleaner  10  also comprises a thermal cutoff assembly  221  (FIG. 8) utilizing a temperature sensitive safety switch that terminates operation of the suction motor  210  is an excessively high temperature is sensed. The motor  210  cannot be restarted until the switch and sensing unit cool and the electrical circuit is broken and connected again, i.e. the switch is reset. That is, both cooling and reset must occur before the motor  210  can be restarted. The thermal cutoff assembly  221  comprises a switching element having a positive temperature coefficient characteristic. The switching element is preferably mounted on the shroud  220  of the suction motor  210  and is wired in series therewith to automatically shut off the motor  210  if excessively high temperatures are sensed or an overheat condition occurs. Overheating may occur if one or more of the filters  270 ,  260  or  60  become blocked or excessively plugged, thereby hindering or precluding airflow past the suction motor  210 . The motor  210  cannot be restarted until the switching element cools and the electrical circuit is re-established. The electrical circuit is re-established in one of several ways such as by unplugging the vacuum cleaner or turning the power switch off, and then either plugging in the vacuum cleaner or turning the power switch on. The positive temperature coefficient characteristic of the switching element provides an advantage over conventional manual reset thermal cutoff assemblies in that it simplifies the design and eliminates parts otherwise required such as a restart button and related wiring.  
         [0054]    Most preferably, the thermal cutoff assembly comprises a positive temperature coefficient resistor and a reset component. The positive temperature coefficient resistor is adapted to switch, at a predetermined temperature such as indicative of overheating or a clogged filter, from a low resistance to a very high resistance. When the positive temperature coefficient resistor switches to a high resistance, the cutoff assembly cuts off electric power to the motor assembly. The reset component prevents the restoration of power to the motor assembly until electric power is disconnected from the cutoff assembly, such as by unplugging the unit or turning the power switch off, and the positive temperature coefficient resistor changes back to a low resistance while the unit is disconnected. The change to a low resistance occurs as a result of sufficient cooling of the positive temperature coefficient resistor. Only then may electric power be directed to the motor.  
         [0055]    The preferred embodiment vacuum cleaner  10  utilizes a reliable mounting configuration and technique for attaching the handle  90  to the upper portion of the vacuum cleaner  10 . Referring to FIG. 1A, the handle  90  is mounted between the upper portion of the rear housing  20  and the front cover  30 . Specifically, the lower region of the handle proximate to a lower distal end  95  is placed within a handle cradle  24  provided on the upper interior surface of the rear housing  20 . One or more outwardly extending mounting posts  26  are provided, preferably along the length of the mounting cradle  24 . It is also preferred to provide a mounting post  26  at the uppermost region of the rear housing  20  to further secure the handle  90 . One or more mounting apertures  96  are defined along the lower portion of the handle  90  such that when the handle  90  is placed within the cradle  24 , the mounting posts  26  are aligned with the apertures  96  and extend therein. The handle  90  is secured to the rear housing  20  by attaching the rear cover  30  over the handle  90  disposed and aligned within the cradle  24 . It is also contemplated that a similar cradle may be provided on the interior surface of the front cover  30 , preferably with mounting posts that would engage additional mounting apertures defined in the handle  90 .  
         [0056]    The preferred embodiment vacuum cleaner  10  utilizes a transmission control cable configuration substantially as shown in U.S. Pat. No. 4,249,281. Referring to FIGS. 1A, 2B, and  13 , it will be noted that the transmission neutral lock mechanism  130  is disposed on the handle  90  and the transmission  240  is disposed within the upper and lower bases  40  and  180 , respectively. The handle assembly comprising the cover  102  and the grip  100  is preferably of a plastic material and is clamped together by means of screws  950  and  952 . For this purpose suitable slots  954  may be provided on opposite sides of the upper end  91  of the handle  90  through which losses  956  and  958  extend to engage one another. This mounting thereby covers the upper end of the handle  90  and inhibits removal of the handle assembly therefrom and yet permits the handle assembly to move slidably axially at the end of the handle  90 . This mounting of course also inhibits relative rotation between the handle assembly and the handle  90 .  
         [0057]    A further slot  960  is provided extending axially and adjacent the end  91  of the handle  90  and a boss  962  extends centrally into this slot from the handle cover  102 . Helical springs  132  are affixed to opposite sides of the boss  962  and extend in opposite directions for connection to the insides of the handle  90  at opposite ends of the slot  960 . The springs  132  serve to hold the handle assembly at a central position with respect to the slot  960 , while permitting resilient movement back and forth therefrom, depending upon the forces applied to the handle assembly.  
         [0058]    In addition, an axially extending slot  964  may be provided at one end of the handle assembly, with a groove  966  underlying the slot  964  and having somewhat greater dimensions. The mechanism  130  is slidably mounted with an enlarged base in the groove  966  and a push-button end extending through the slot  964 . A leaf spring  968  extends in the groove  966  between the handle  90  and the mechanism  130 , and has one end thereof fixed with respect to the cover  102 , for example by extending into a radially outwardly extending aperture  970  at the end of the groove  966 . The other end of the leaf spring  968  is formed with a projection  972  toward the handle  90 , the projection  972  being aligned with a hole  974  in the wall of the handle  90  in the central or neutral position of the handle assembly. The spring  978  is normally biased away from the hole  974 , with the button in pocket of the slot, but when the button is depressed and urged to a forward position it depresses the spring  978  so that the projection  972  enters the hole  974 , to inhibit relative sliding movement of the handle assembly with respect to the handle  90  from the neutral position.  
         [0059]    Still referring to FIG. 13, the Bowden wire  131  extends to a suitable clamp  980  adjacent the upper end of the handle assembly. A central wire  982  of the cable has an enlarged upper end  984  which is restrained at the end of the handle assembly. As a consequence, forward or rearward movement of the handle assembly will cause the central wire  982  to slip forwardly and rearwardly within the outer sheath.  
         [0060]    The sheathed cable extends from the selector  130  downward through the handle  90  and into the upper portion of the vacuum cleaner  10 , i.e. between the rear housing  20  and the front cover  30 . The sheathed cable extends further toward the bottom portion of the rear housing  20 , and particularly proximate to the pivot hub  350  provided on the first side wall  310  of the rear housing  20 . The sheathed cable extends through its pivot hub  350  and into the base of the vacuum cleaner  10 . The cable is connected to a transmission shifting yoke that utilizes a linearly displaceable shifting member which effects shifting to the transmission  240 . The active or movable end of the cable is attached to the shifting member and the end of the sheath is attached to a stationary support post provided in the vicinity of the shifting member. In the assembled vacuum cleaner  10 , movement of the selector  130  is transmitted to the displaceable shifting member by the control cable.  
         [0061]    The present invention vacuum cleaner  10  utilizes an elegant locking and affixment configuration between the upper hose  70  and the upper portion of the vacuum cleaner  10 . FIG. 11 is a detail of the hose adapter  71  and its engagement with the upper portion of the rear housing  20 . As shown in FIG. 1A, the hose adapter  71  is disposed between the upper hose  70  and the rear housing  20 . Referring to FIGS. 11 and 11A, the hose adapter  71  preferably comprises an inclined lip or flange  600  extending around at least a portion of the outer periphery of the adapter  71 . The lip  600  has an inclined or ramped region designated herein as a cam region  610 . The distal end  630  of the hose adapter  71  is inserted within an opening  660  defined in a support ledge  620 , generally provided along the interior facing side of the rear housing  20 . The bag filter  270  is attached to the end  630  by fitting the end  630  into an aperture  270 A in a mounting plate  270 B provided at the top of the filter  270 . The mounting plate is retained between the support ledge  620  and a parallel ledge  620 A. The opening  660  may be an aperture of circular shape, or may be in the form of a notched passageway defined in the support of ledge  620 . One or more support ribs  650  may be provided to strengthen the attachment between the lip  600  and the hose adapter  71 . The hose adapter  71  is releasably engaged with the rear housing  20  by positioning it over the opening  660  such that the lip  600  is disposed underneath a locking ledge  640 . That is, a portion of the lip  600  is disposed between the locking ledge  640  and the support ledge  620 . The hose adapter  71  is then rotated, which due to the action of the inclined cam region  610 , induces downward displacement of the hose adapter  71 , and specifically the distal end  630 , into the opening  660 . The lip  600  defines an arcuate edge  604  extending around at least a portion of the hose adapter  71 . It is preferred to provide a flat region  602  such that when the hose adapter  71  is locked into place upon the support ledge  620 , the flat edge  602  is flush, or at least not extending beyond, an outer edge  622  of the support ledge  620 . The arcuate edge  604  of the lip  600  preferably extends radially outward from the hose adapter  71  a distance such that when the adapted  71  is not locked into place, i.e. and so that the flat edge  602  is not flush with the outer edge  622  of the support ledge  620 , the arcuate edge  604  extends outward beyond the edge  622 . This prevents the bag cover  80 , or other housing component, from being fully engaged with the rear housing  20 . This unique interlock configuration requires that the upper hose  70  be properly coupled to the housing of the vacuum cleaner  10 .  
         [0062]    The preferred embodiment vacuum cleaner  10  also utilizes a single wheel drive mechanism. The use of a single wheel drive mechanism offers improved maneuverability, a more economical and less expensive drive assembly, simplicity of engaging the transmission to the chassis, versatility of location relative to the cleaning head or base, and improved serviceability for the vacuum cleaner.  
         [0063]    The drive assembly and related gear cluster is preferably of the type disclosed in U.S. Pat. No. 4,249,281 to Meyer et al., which is herein incorporated by reference. Furthermore, it is contemplated that the drive motor used in the preferred embodiment vacuum cleaner  10  could be of the variable speed type, controlled by an electronic, module, which may be in the form of a diode in series or a potentiometer. This would enable the drive speed to be operator adjustable for the pace desired by each individual user of the vacuum cleaner  10 .  
         [0064]    As may be seen most clearly in FIG. 12, the single wheel drive mechanism comprising the drive motor  230 , the transmission  240 , and associated gear cluster and single drive wheel preferably disposed and mounted within the lower base  180 . Mounting provisions may be provided on a side region of the lower base  180 , such as the left hand side of the lower base  180  illustrated in FIGS. 1A and 12. A drive shaft is used to couple the single drive wheel  241  to the other components of the drive mechanism. Various supporting and mounting provisions can be provided in the lower base  180  for rotatably securing the drive shaft and single drive wheel to the lower base  180 . Preferably in this regard, an “eyebrow” notch is formed in a vertical wall or rib in the lower base  180 , through which the drive shaft passes. The shaft may be further supported by a bearing disposed within the notch.  
         [0065]    It is also contemplated to utilize a clutch in the drive mechanism. A problem encountered in self-propelled vacuum cleaners is fracturing or breaking or other failures in the weakest component in the gear chain. This often results during unpowered, rolling transport of the vacuum cleaner, when the user has failed to place the drive mechanism in neutral. Under these conditions, torque generated by the drivewheel rolling across the floor is transmitted through the drive axle to the transmission and eventually to the drive motor. In the event the total gear reduction is relatively high, so that the drive motor will tend to not turn, the weakest component in the gear chain will fail. In order to remedy this problem, a one-way clutch is added to the drive train to disconnect the torque between the transmission and the drive module gear reduction assembly or drive motor.  
         [0066]    The drive mechanism utilized in the preferred embodiment vacuum cleaner  10  is assembled by utilizing a unique technique for achieving proper spacing between the legs of a yoke and the drive gear cluster. Referring to the noted U.S. Pat. No. 4,249,281, and particularly to FIGS. 5 and 6 of that patent, a yoke 120 generally encloses the gear cluster. As described in that patent, a plurality of bearing rivets 130 are provided on downwardly extending arms 124 of the yoke 120. These rivets 130 are utilized to effect proper spacing between the yoke arms 124 and the gear cluster. Although the assembly described in the &#39;281 patent is satisfactory in many respects, the present invention provides an improved assembly that is significantly easier to assemble and eliminates the necessity for the bearing rivets 130.  
         [0067]    As noted, it is important to achieve proper spacing between the ends of the gear cluster and arms of the yoke. In accordance with the present invention, one or more spacing washers are incorporated in the assembly. The width and placement of the washers are such that the gear cluster is placed into proper position with respect to the yoke arms. During assembly, the yoke and the gear cluster are introduced into a machine that automatically measures the total axial thickness of the gear cluster, and also measures the interior clearance or distance between the yoke arms. Using these two measured distances, one or more spacing washers are then dispensed and preferably appropriately incorporated into the gear cluster to arrive at a proper spacing between the gear cluster and yoke arms.  
         [0068]    Proper neutral adjustment is preferably accomplished by utilizing one or more spacers, i.e. spacing shims, that are inserted in or between a centering plate of the gear cluster. A single set screw, preferably extending through the yoke, is then tightened to lock the gear cluster, now in its spaced and neutral position, in place with the yoke. Upon incorporation into the vacuum cleaner, and connection to a Bowden wire or control cable  131 , the shims are removed and the set screw loosened or also removed.  
         [0069]    As further illustrated in FIG. 12, the drive motor  230  and the transmission  240  are encased in a shroud  700 . Carbon (or other) dust particles produced by the motor and transmission are prevented from escaping to the environment by providing a suction in the area of the drive motor to draw particles into the airflow which passes ultimately through the finial filter  60 . The airflow over the drive motor and the transmission is drawn through openings in the shroud  700 . This suction is provided by the vacuum motor  210  that provides suction for cleaning as its primary function. According to a preferred embodiment a slot opening  702  is provided in the shroud  700  which communicates with the main floor nozzle chamber.  
         [0070]    While the foregoing details are what is felt to be the preferred embodiments of the present invention, no material limitations to the scope of the claimed invention are intended. Further, features and design alternatives that would be obvious to one of ordinary skill in the art are considered to be incorporated herein. The scope of the invention is set forth and particularly described in the claims herein below.