Abstract:
A wheel assembly for a self-propelled apparatus such as a vacuum cleaner is disclosed. The self-propelled apparatus includes a drive motor, a drive axle coupled to the drive motor, and at least one drive wheel assembly. The drive wheel assembly includes a drive member rotatably secured to the drive axle, an outer wheel casing at least partially surrounding the drive member, and a resilient coupling mechanism for establishing a rotational engagement between the drive member and the outer wheel casing after a predetermined amount of rotation of the drive member relative to the outer wheel casing.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to wheel constructions. It finds particular application in conjunction with a resiliently-coupled drive wheel assembly for a self-propelled vacuum cleaner, and will be described with particular reference thereto. However, it should be appreciated that the wheel constructions disclosed herein can find use in a variety of other applications.  
           [0002]    Self-propelled vacuum cleaners are well-known in the art. In a typical self-propelled upright vacuum cleaner arrangement, a transmission assembly associated with a floor nozzle assembly mechanically transfers rotational power from an electric motor to a drive axle. The drive axle supports powered or otherwise driven wheels at opposing ends thereof. The driven wheels are directly connected to or otherwise fixed for positive mechanical rotation with the drive axle. A control mechanism associated with the transmission assembly governs the direction of rotation of the drive axle, and hence, the direction of travel of the vacuum cleaner. The control mechanism is typically actuated by articulating or pivoting the upright handle portion of the vacuum cleaner relative to the floor nozzle to effectuate either forward or reverse travel of the vacuum cleaner.  
           [0003]    One problem associated with the illustrated drive arrangement is that when the upright handle portion is pivoted about the floor nozzle portion, the direct mechanically coupling of the electric motor output shaft to the drive wheels results in an abrupt or sudden start or acceleration of the vacuum cleaner in either the forward or reverse directions. Such “jump starts” can be disturbing to the user during a vacuuming operation.  
           [0004]    Accordingly, it has been considered desirable to develop a new and improved drive wheel assembly for a self-propelled vacuum cleaner that meets the above-stated needs and overcomes the foregoing difficulties and others while providing better and more advantageous results.  
         SUMMARY OF THE INVENTION  
         [0005]    In accordance with one aspect of the present invention, a wheel assembly is disclosed for a vacuum cleaner that has a drive axle mechanically coupled to a drive source. The wheel assembly includes a drive member rotatably secured to the drive axle, a wheel casing at least partially surrounding the drive member, and a resilient coupling that establishes a rotational engagement between the drive member and the wheel casing after a predetermined amount of rotation of the drive member relative to the wheel casing.  
           [0006]    In accordance with another aspect of the present invention, a self-propelled vacuum cleaner is disclosed. The self-propelled vacuum cleaner includes a drive motor, a drive axle coupled to the drive motor, and at least one drive wheel assembly including a drive member rotatably secured to the drive axle, an outer wheel casing surrounding the drive member, and a resilient coupling that establishes a positive rotational engagement between the drive member and the wheel casing after the predetermined amount of rotation of the drive member relative to the wheel casing.  
           [0007]    In accordance with yet another aspect of the present invention, a method is disclosed for propelling a vacuum cleaner that includes a drive motor, a drive axle coupled to the drive motor, and at least one drive wheel assembly having a drive member rotatably secured to the drive axle, an outer wheel casing surrounding the drive member, and a resilient coupling that establishes a positive rotational engagement between the drive member and the wheel casing after the predetermined amount of rotation of the drive member relative to the wheel casing. The method includes rotating the drive axle and the drive member while maintaining the outer wheel casing stationary for a predetermined period of time, and establishing a positive rotational engagement between the drive member and the outer wheel casing after the predetermined period of time has elapsed to cause the outer wheel casing to rotate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments of the invention and are not to be construed as limiting the same.  
         [0009]    [0009]FIG. 1 is a front elevational view of an exemplary upright vacuum cleaner that incorporates a drive wheel assembly according to the present invention;  
         [0010]    [0010]FIG. 2 is an enlarged, exploded view of a first embodiment of the drive wheel assembly of FIG. 1 from a first perspective;  
         [0011]    [0011]FIG. 3 is an exploded view of the drive wheel assembly of FIG. 2 from a second perspective;  
         [0012]    [0012]FIG. 4 is an exploded view of the drive wheel assembly of FIG. 2 from a third perspective;  
         [0013]    [0013]FIG. 5 is a side elevational view of the drive wheel assembly of FIG. 2 in an assembled configuration;  
         [0014]    [0014]FIG. 6 is a section view of the drive wheel assembly of FIG. 5 taken along line  6 - 6 ;  
         [0015]    [0015]FIG. 7 is a section view of the drive wheel assembly of FIG. 6 taken along line  7 - 7 ;  
         [0016]    [0016]FIG. 8 is a section view of the drive wheel assembly of FIG. 5 taken along line  8 - 8 ;  
         [0017]    [0017]FIG. 9 is a side elevational view of a second embodiment of a drive wheel assembly according to the present invention;  
         [0018]    [0018]FIG. 10 is a section view of the drive wheel assembly of FIG. 9 taken along the line  10 - 10 ; and  
         [0019]    [0019]FIG. 11 is an exploded perspective view of the drive wheel assembly of FIG. 9. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodiments of the invention only and not for purposes of limiting same, FIG. 1 shows an exemplary upright vacuum cleaner housing A having an upright handle assembly B including a dirt holding chamber, and a floor nozzle assembly C. The upright handle assembly B is joined to the floor nozzle assembly C by conventional pivot means D. In the embodiment being described, the floor nozzle assembly C includes two powered or otherwise driven wheel assemblies  10  and two non-powered wheel or caster assemblies  12 . While the vacuum cleaner A is illustrated as being of an upright type, it should be appreciated by those of average skill in the art that the wheel construction illustrated herein can also be employed for use on canister-type vacuum cleaners, wet/dry vacuum cleaners, carpet extractors, etc., and in a variety of other wheeled environments.  
         [0021]    With reference now to FIG. 2, each wheel assembly  10  includes a drive member  14 , a wheel housing  16 , and a wheel housing cover  18 . The wheel housing  16  and the wheel cover  18  can be collectively referred to as an outer wheel casing. The wheel housing  16  is formed from a cylindrical side wall  20  and, as best shown in FIG. 3, a disk-shaped end wall  22 . Located on a free edge of the cylindrical side wall  20  is an annular flange  24 . With continued reference to FIG. 3, a central aperture  26  extends through the end wall  22 . Referring to FIG. 4, the aperture  26  is adapted to receive a bearing  28 . In the embodiment being described, the bearing  28  is an oil impregnated, sintered bronze radial bearing.  
         [0022]    Referring again to FIG. 2, the wheel cover  18  is formed as a circular disk having a cylindrical side wall  30 , an outer surface  32   a , and, as shown in FIG. 4, an inner surface  32   b . With continued reference to FIG. 4, an annular slot  34  is defined in the inner surface  32   b  proximate the side wall  30 . With reference to FIG. 7, the slot  34  is sized and shaped to accommodate the annular flange  24  of the wheel housing  16  in an assembled state of the wheel assembly  10 . As such, the wheel housing  16  and the wheel cover  18  cooperate to enclose or otherwise surround the drive member  14 . Referring again to FIGS. 2 and 3, a central aperture  36  extends through the center of the wheel cover  18 . The aperture  36  is adapted to receive a bearing  38  such as an oil impregnated, sintered bronze radial bearing.  
         [0023]    With continued reference to FIGS.  2 - 4 , the drive member  14  is generally formed as a spool or reel with first and second disk-shaped end walls  40 ,  42  and a reduced-diameter cylindrical portion  44  located between them. As such, a circumferential channel or groove  45  is defined in the member  14 . Further, a central aperture  46  extends axially through the member  14 . As shown in FIG. 2, a transverse groove or channel  48  is defined in the first end wall  40 . The transverse groove  48  communicates with the aperture  46 . As shown in FIG. 4, an arcuate or C-shaped (i.e. semi-circular) groove or channel  50  is defined in the second end wall  42 .  
         [0024]    The drive member  14  is coupled to the wheel housing  16  and wheel cover  18  by a resilient coupling including a resistance means. In the embodiment being described, the resistance means takes the form of at least one, and preferably two or more, elastic members  52 ,  54  such as coil springs and the like. As best shown in FIG. 6, each coil spring  52 ,  54  includes fastening means associated with each end thereof. The fastening means takes the form of inner and outer hook-shaped end portions  56 ,  58 , respectively of each coil spring. The inner hook portion  56  of each spring is retained within the annular groove  45  by a transverse pin  60  that extends through corresponding apertures  62  associated with each end wall  40 ,  42 . The apertures  62  are spaced approximately 180° apart. Likewise, the outer hook portion  58  of each spring is supported by a transverse pin  64  that extends through corresponding apertures  66  associated with the wheel housing  16  and the wheel cover  18 . The apertures  66  are also spaced approximately 180° apart.  
         [0025]    As best shown in FIG. 3, a wheel drive pin  68  is mounted in an aperture  70  associated with the wheel housing end wall  22 . A free end of the wheel drive pin  68  projects into the arcuate channel  50  associated with the end wall  42  in an assembled state of the wheel assembly  10 .  
         [0026]    Referring again to FIG. 2, the radial bearings  28 ,  38  and the aperture  46  are axially aligned to rotatably support a drive axle  72  of the vacuum cleaner A. As best shown in FIG. 7, a free end of the drive axle  72  includes a transverse notch  74  that accommodates a drive pin or key  76  positioned within the channel  48  associated with the end wall  40 . Accordingly, the drive pin  76  transfers power from the drive axle  72  to the drive member  14  during operation of the vacuum cleaner.  
         [0027]    Referring now to FIG. 8, in a “resting” or equilibrium state of the wheel assembly  10  (i.e. the drive axle  72  is not applying rotational power to the drive member  14 ), there is minimal or no spring force generated by the springs  52 ,  54 , and the free end of the wheel drive pin  68  is substantially centered along the length of the arcuate notch  50  in the end wall  42 .  
         [0028]    Power is directly coupled from the drive axle  72  to the drive member  14 , via the drive pin  76 , when the vacuum cleaner drive control mechanism is actuated (such as by pivoting the vacuum cleaner upright handle portion C forward or backward relative to the floor nozzle portion B). During initial rotation of the drive member  14 , the depending arcuate notch  50  rotates relative to the stationary wheel drive pin  68 , and the elastic members  52 ,  54  are increasingly tensioned or otherwise stretched to apply a gradually increasing torque force to the outer wheel casing.  
         [0029]    Continued rotation of the drive member  14  results in driving an end wall of the arcuate notch  50  into contact with the wheel drive pin  68  against a tension force generated by the elastic members  52 ,  54  to effectuate a positive rotational engagement between the drive member  14  and the wheel housing  16  and wheel cover  18 . The velocity with which the notch end wall impacts the wheel drive pin  68  can be controlled (i.e. reduced) by purposeful selection of the elastic characteristics of the elastic members  52 ,  54 .  
         [0030]    It is recognized that the gradual application of torque results in a less abrupt acceleration of the vacuum cleaner. That is, a predetermined time period elapses from the instant that the drive control mechanism is actuated to the point that positive rotational engagement of the outer wheel casing is established. During this time period, the elastic members are gradually tensioned and a torque force is gradually applied to the outer wheel casing. Accordingly, actuation of the drive wheel assembly  10  in response to an input from the vacuum cleaner drive control mechanism is controlled by i) providing a delay interval from the moment that the drive control mechanism is actuated, and ii) gradually increasing a torque force to the outer wheel casing to the point that a positive rotational engagement is established.  
         [0031]    It is further recognized that a certain amount of backlash (such as with a clutch, etc.) can be designed into vacuum cleaner drive train (including the drive wheel assembly) so that when power to the drive axle  72  is suspended (such as when moving the vacuum cleaner drive control mechanism from a first drive position—such as forward—to a neutral position, or through the neutral position to a second drive position—such as backward), a centering force is generated by the springs  52 ,  54 . The centering force causes the drive member  14  to slightly rotate relative to the outer wheel casing thereby repositioning (i.e. centering) the inner arcuate channel  50  relative to the wheel drive pin  68 . Thereafter, a subsequent actuation of the drive control mechanism results in establishing a time-delayed and less abrupt engagement of the drive wheel assemblies  10  as described above.  
         [0032]    It is contemplated that each of the drive member  14 , wheel housing  16 , wheel cover  18 , and associated pins  60 ,  64 ,  68 , and  70  can be manufactured (e.g. molded, cast, turned, stamped, machined, cut, etc.) from suitable materials, such as a plastic material, a composite material, a resin material, a metal material, a wood material, etc. Further, the side walls  20 ,  30  defining outer wheel casing can include a textured (e.g rubberized) surface or a layer of tread material to improve the traction of the wheel assemblies  10 .  
         [0033]    It should be recognized that suitable screws, bolts, nails, cotter pins, etc. can be used in place of any one or more of the pins  60 ,  64 ,  68 , and  70 . The springs  52 ,  54  are preferably formed from steel. It should also be recognized that resistance means other than coil springs  52 ,  54  can be utilized to reduce the velocity with which the drive member  14  impacts the wheel drive pin  68  to establish positive rotational engagement.  
         [0034]    Further, it should be recognized that if the tension forces generated by the stretched springs  52 ,  54  are strong enough, it is possible that a rotational connection between the drive member and the wheel housing can be established by the springs alone without the positive rotational engagement that is provided by the channel  50  and the wheel drive pin  68 . In either case, as the springs  52 ,  54  are increasingly tensioned, torque is gradually applied to the outer wheel casing.  
         [0035]    A further embodiment of a driven wheel assembly  110  according to the present invention is shown in FIGS.  9 - 11 , where reference numerals offset by a factor of  100  are used to denote the same or similar components of the wheel assembly  10  described and illustrated in FIGS.  1 - 8 .  
         [0036]    With particular reference now to FIG. 11, the wheel assembly  110  includes a drive member  114 , a wheel housing  116 , and a wheel housing cover  118 . The wheel housing  116  and the wheel cover  118  is collectively referred to as an outer wheel casing. The wheel housing  116  is formed from a cylindrical side wall  120  and a disk-shaped end wall  122  that cooperate to define a contoured open cavity  180 . A central aperture (such as e.g.  26 , FIG. 3) extends through the end wall  122  and is sized and shaped to receive at least one of a radial bearing  128  and a radial fluid seal  182  (in the case of one embodiment of the invention described further below).  
         [0037]    A plurality of projections  184  are formed integral with the cylindrical side wall  120  and extend radially inward from an inner surface thereof within the open cavity  180 . As best shown in FIG. 10, in the embodiment being described, four projections  184  are circumferentially-spaced approximately 90° apart from each other to define four chamber portions  186  that generally converge at a central cavity portion  188 . The width of each projection  184  tapers in a radially inward direction, and the side surface of each projection is shaped or otherwise contoured to define a land or seat  190 .  
         [0038]    Referring again to FIG. 11, the wheel cover  118  is formed as a circular disk. A central aperture  136  through the cover  118  is adapted (i.e. sized and shaped) to receive at least one of a bearing  138  (such as an oil impregnated, sintered bronze radial bearing) and a second fluid seal  182 . (FIG. 9). It is contemplated that the wheel cover  118  can include a cylindrical side wall (e.g.  30 , FIG. 4) with an annular slot (e.g.  34 , FIG. 4) that is sized and shaped to accommodate an annular flange (such as e.g.  24 , FIG. 4) of the wheel housing to enclose and/or seal the drive member  114  within the housing cavity  180 . Alternatively, the wheel cover  118  can mate with a planar open end surface of the wheel housing  116  and be positively secured thereto with conventional attachment means such as nuts, bolts, screws, adhesive, threads, etc. In both cases, a gasket (not shown) can be interposed between the wheel cover  118  and the open end surface of the wheel housing  116  to provide a fluid-tight seal therebetween.  
         [0039]    With continued references to FIGS. 10 and 11, the drive member  114  is generally formed as an impeller with a plurality of vanes  192  extending radially outward from a central hub  194 . A passage or aperture  146  extends axially through a side wall defining the central hub  194 . In the embodiment being described, four vanes  192  are circumferentially-spaced approximately 90° apart from each other. The width of each vane  192  tapers in a radially inward direction, and the side surface of each vane is shaped or otherwise contoured to define a land or seat  196 .  
         [0040]    Referring again to FIG. 9, in an assembled state of the Gwheel assembly  110 , the fluid seals  182  and/or radial bearings  128 ,  138  are axially aligned with the drive hub passage  146  and rotatably support a drive axle  172  of the vacuum cleaner. The drive member  114  is rotatably secured to, or otherwise fixed for rotation with, the drive axle  172 . The drive axle  172  can be splined, threaded, keyed, etc. to fixedly secure the drive member  114  to the axle  172 . As best shown in FIG. 10, the wheel housing chamber portions  186  each accommodate a respective drive member vane  192  while the central cavity portion  188  of the wheel housing  116  accommodates the drive member central hub  194 . The drive member  114  is coupled to the wheel housing  116  by a resilient coupling including at least one of a resistance means and a damping means.  
         [0041]    In the embodiment being described, the resistance means takes the form of at least one, and preferably two or more (e.g. four), elastic members  152  such as coil springs and the like, and the damping means takes the form of at least one, and preferably two or more (e.g. four), damping members  198  such as dashpots and the like. The damping means can also take the form of a fluid  200  within the cavity  180 . In such as case, the seals  182  prevent such fluid from leaking from the cavity  180 . It should be appreciated that, within a specified operating range, the elastic members  152  provide a directly proportional and substantially linear resistance versus displacement characteristic, whereas the damping members  198  or damping fluid  200  provide a directly proportional and substantially linear resistance versus velocity characteristic.  
         [0042]    Each of the at least one elastic members  152  is interposed between the mutually opposed lands  190 ,  196  of the wheel housing projections  184  and drive member vanes  192 , respectively. It is contemplated that the lands  190 ,  196  can be recessed or otherwise bored to retain respective ends of a coil spring. Alternatively, a retainer pin(s)  202  can project from one or both lands  190 ,  196  to hold a coil spring in place between a projection  184  and an adjacent drive member vane  192 . Likewise, each of the at least one damping members  198  is interposed between the mutually opposed lands  190 ,  196  of the projections  184  and drive member vanes  192 , respectively. It is contemplated that the lands  190 ,  196  can be recessed or otherwise bored to retain respective ends of a damping member. Further, maintaining the elastic members  152  and damping members  198  in slight compression at a resting state of the wheel assembly  110  assists in maintaining the position of the respective elastic and damping members  152 ,  198  between the drive member  114  and wheel housing  116 .  
         [0043]    It is contemplated that the wheel assembly  110  can be configured with at least two elastic members  152 , or with at least two damping members  198 , or preferably, with a combination of elastic members  152  and damping members  198 . For instance, in the embodiment illustrated in FIG. 10, the wheel assembly  110  includes four elastic members  152  and four damping members  198  with i) a first chamber portion  186  housing two elastic members  152  on opposing sides of a first drive member vane  192 , ii) a second chamber portion  186  housing two damping members  198  on opposing sides of a second drive member vane  192 , and iii) third and fourth chamber portions  186  housing an elastic member  152  and a damping member  198  on opposing sides of third and fourth drive member vanes  192 , respectively.  
         [0044]    [0044]FIG. 10 illustrates a resting or equilibrium state of the wheel assembly  110 . That is, the drive axle  172  is not applying rotational power to the drive member  114 . Accordingly, there are no tension forces and compression forces, or at least minimal and substantially equal tension forces and compression forces, generated by the elastic members  152  and damping members  198  such that the drive member vanes  192  are substantially centered within the respective wheel housing chamber portions  186 . A rotational force is directly coupled from the drive axle  172  to the drive member  114  when the vacuum cleaner drive control mechanism is actuated (such as by pivoting the vacuum cleaner upright handle portion C forward or backward relative to the floor nozzle portion B).  
         [0045]    During initial rotation of the drive member  114 , the elastic members  152  and damping members  198  located on the leading edge of each drive member vane  192  are compressed, while the elastic members  152  and damping members  198  located on a trailing edge of each drive member vane  192  are tensioned. Continued rotation of the drive member  114  results in gradually increasing the compressive and tensile forces acting on the elastic members  152  and/or the damping members  198 , and hence a gradually increasing torque force acting on the wheel housing until a positive rotational engagement between the drive member  114  and the wheel housing  116  is established. This generally occurs when the rotational driving force acting on the drive member  114  overcomes the compressive and/or tensile forces generated by the elastic members  152  and/or the damping members  198 .  
         [0046]    Positive rotational engagement can occur when the leading edge elastic elements and/or damping elements are fully compressed, or can occur at some point less than full compression of the elastic elements and/or damping elements. In either case, the abruptness with which a positive rotational engagement between the drive member  114  and the wheel housing  116  is established can be controlled by purposeful selection of the elastic characteristics of elastic members  152  and of the damping characteristics of the damping members  198 . Accordingly, actuation of the drive wheel assembly  110  in response to an input from the vacuum cleaner drive control mechanism is controlled by gradually applying a torque force to the wheel housing  116  over a predetermined period of time.  
         [0047]    Referring again to FIG. 10, the damping means can be a fluid within the housing cavity  180 . In such case the level of damping provided by such fluid can be regulated by i) the viscosity of the damping fluid, and/or ii) throttling the flow of fluid within the cavity  180 , such as through one or more channels  210  defined between the ends of each drive member vane  192  and the inner surface of housing side wall  120 , and/or through one or more channels  212  defined between the ends of each housing projection  184  and the drive member center hub  194 .  
         [0048]    The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.