Abstract:
An upright vacuum cleaner includes a nozzle assembly, a canister assembly pivotally mounted to said nozzle assembly, a suction fan and drive motor and a biaser. The biaser has a first end that engages the nozzle assembly and a second end that engages the canister assembly. The biaser provides a positive downforce urging the forward end of the nozzle assembly toward the surface being cleaned.

Description:
This application is a divisional of U.S. patent application Ser. No. 10/090,656, filed on Mar. 5, 2002 now U.S. Pat. No. 6,772,474 which claims the benefit of U.S. Provisional Patent Application No. 60/275,065 filed on Mar. 12, 2001. 

   TECHNICAL FIELD 
   The present invention relates generally to the vacuum cleaner art and, more particularly, to an upright vacuum cleaner incorporating a spring loaded nozzle. 
   BACKGROUND OF THE INVENTION 
   Upright vacuum cleaners in all of their designs and permutations have become increasingly popular over the years. The upright vacuum cleaners generally incorporate a nozzle assembly and a canister assembly pivotally mounted to the nozzle assembly. Wheels on the nozzle and canister assemblies allow the vacuum cleaner to smoothly ride over the surface to be cleaned. 
   The canister assembly includes an operating handle that is manipulated by the user to move the vacuum cleaner back-and-forth across the floor. The canister assembly also includes either a bag-like filter or a cyclonic separation chamber and filter combination that trap dirt and debris while substantially clean air is exhausted by a fan that is driven by an onboard electric motor. It is this fan and motor arrangement that generates the drop in air pressure necessary to provide the desired cleaning action. 
   In most upright vacuum cleaners sold today, a rotary agitator is also provided in the nozzle assembly. The rotary agitator includes tufts of bristles, brushes, beater bars or the like to beat dirt and debris from the nap of a carpet being cleaned while the pressure drop or vacuum is used to force air entrained with this dirt and debris into the nozzle of the vacuum cleaner. 
   As the vacuum cleaner is manipulated back-and-forth by the operator with the handle on the canister assembly, the nozzle assembly is periodically lifted slightly from the floor. This lifting action adversely affects the cleaning efficiency of the vacuum cleaner. Further, during the cleaning of certain surfaces there is a tendency for vibration to develop in the vacuum cleaner as a result of the engagement of the rotary agitator against the particular surface being cleaned. This vibration is often transmitted through the control handle and is often annoying to the user. A need is therefore identified for an upright vacuum cleaner that addresses these problems in a manner to provide enhanced cleaning efficiency as well as vibration reduction. 
   SUMMARY OF THE INVENTION 
   In accordance with the purposes of the present invention as described herein, an improved upright vacuum cleaner is provided. That vacuum cleaner includes a nozzle assembly and a canister assembly pivotally mounted to the nozzle assembly. A suction fan and motor are carried on one of the nozzle assembly and the canister assembly. Additionally, the upright vacuum cleaner includes a means, such as a biaser, having a first end engaging the nozzle assembly and a second end engaging the canister assembly. This biaser provides a positive downforce urging a forward end of the nozzle assembly toward the surface to be cleaned. This urging not only enhances cleaning efficiency but also serves to dampen vibration. 
   In accordance with additional aspects of the present invention, the biaser may be a torsion spring. Further, the nozzle assembly may include a hollow stub shaft received within a cooperating groove in the canister assembly. That stub shaft defines an axis for pivoting movement of the canister assembly with respect to the nozzle assembly as the vacuum cleaner is manipulated by the user. At least a portion of the spring is received in this hollow stub shaft. 
   Still further, the canister assembly may include a channel adjacent the groove and the second end of the spring is elongated and received in that channel. The channel may be formed, for example, by a box rib on the wall of the canister assembly. Additionally, the hollow stub shaft may include a slot in the side wall thereof through which the end of the spring extends into the channel. 
   The spring is selected to provide between about 1.2 and about 3.2 lbs/sq. in. of preload and more typically between about 2.0 and about 2.4 lbs/sq. in. of preload. Such a spring provides between about 0.2 and 3.0 lbs/sq. in. of downforce on a forward end of the nozzle assembly. In a typical arrangement, the spring is selected to provide a downforce of between about 0.8 and about 1.6 lbs/sq. in. (e.g. about 1.2 lbs/sq. in.) of downforce on a forward end of the nozzle assembly when the canister assembly is positioned at about a 135° included working angle with respect to the nozzle assembly: that is, when the canister assembly forms an included angle of about 45° with the floor being cleaned. 
   The resulting downforce reduces the vibration of the nozzle assembly and advantageously increases the cleaning efficiency of the vacuum cleaner by maintaining the nozzle assembly in close engagement with the surface being cleaned. This is a particular advantage as vibration may even be controlled in canister and nozzle assemblies constructed from lighter weight materials. Such materials allow the production of more lightweight vacuum cleaners that are particularly favored by consumers since they are easier to handle and require less muscle effort to use. 
   The invention also includes a method of increasing the cleaning efficiency of a vacuum cleaner by providing a downforce on the nozzle assembly of the vacuum cleaner to urge the nozzle assembly toward the floor being cleaned. 
   Still further, the invention also includes a method of reducing vibration in a vacuum cleaner by providing a biasing force between the nozzle assembly and the canister assembly to dampen vibration produced by engagement of the rotary agitator with the surface being cleaned. 
   In the following description there is shown and described one possible embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments, and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The accompanying drawing incorporated in and forming a part of the specification, illustrates several aspects of the present invention, and together with the description serves to explain the principles of the invention. In the drawing: 
       FIG. 1  is a perspective view of an vacuum cleaner constructed in accordance with the teachings of the present invention; 
       FIGS. 2   a  and  2   b  are detailed perspective views from each side showing the positioning of the spring for providing the desired downforce on the nozzle assembly; 
       FIGS. 3   a - 3   c  are detailed, schematical side elevational views showing the orientation of the spring in the hollow stub shaft with the first end engaging the nozzle assembly and the second end engaging a box rib on the canister assembly when the canister assembly is in fully down, operating and fully upright storage positions; and 
       FIG. 4  is a detailed perspective view showing the receipt of the stub shaft on the nozzle assembly in the cooperating notch on the canister assembly. 
   

   Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawing. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Reference is now made to  FIG. 1  showing the upright vacuum cleaner  10  of the present invention. The upright vacuum cleaner  10  includes a nozzle assembly  14  and a canister assembly  16 . The canister assembly  16  further includes a control handle  18  and a hand grip  20 . A control switch  22  is provided for turning the vacuum cleaner on and off. Of course, electrical power is supplied to the vacuum cleaner  10  from a standard electrical wall outlet through a cord (not shown). 
   As is known in the art, sets of front and rear wheels (not shown) are provided, respectively, on the nozzle assembly  14  and canister assembly  16  to support the weight of the vacuum cleaner  10 . Together, these two sets of wheels allow the vacuum cleaner  10  to roll smoothly across the surface being cleaned. To allow for convenient storage of the vacuum cleaner  10 , a foot latch  30  functions to lock the canister assembly  16  in an upright position as shown in  FIG. 1 . When the foot latch  30  is released, the canister assembly  16  may be pivoted relative to the nozzle assembly  14  as the vacuum cleaner  10  is manipulated back-and-forth to clean the floor. 
   The canister assembly  16  includes a cavity  32  adapted to receive and hold a dust bag  12 . Alternatively, the vacuum cleaner  10  could be equipped with a dust collection cup such as found on cyclonic type models if desired. Additionally, the canister assembly  16  carries a suction fan  34  and suction fan drive motor  35 . Together, the suction fan  34  and its cooperating drive motor  35  function to generate a vacuum airstream for drawing dirt and debris from the surface to be cleaned. While the suction fan  34  and suction fan drive motor  35  are illustrated as being carried on the canister assembly  16 , it should be appreciated that they could likewise be carried on the nozzle assembly  14  if desired. 
   The nozzle assembly  14  includes a nozzle and agitator cavity  36  that houses a pair of rotating agitator brushes  38   a ,  38   b . The agitator brushes  38   a ,  38   b  shown are rotatably driven by the drive motor  35  through a cooperating belt and gear drive (not shown). In the illustrated vacuum cleaner  10 , the scrubbing action of the rotary agitator brushes  38   a ,  38   b  and the negative air pressure created by the suction fan  34  and drive motor  35  cooperate to brush and beat dirt and dust from the nap of the carpet being cleaned and then draw the dirt and dust laden air from the agitator cavity  36  to the dust bag  12 . Specifically, the dirt and dust laden air passes serially through one of the hoses  46  and an integrally molded conduit in the nozzle assembly  14  and/or canister assembly  16  as is known in the art. Next, it is delivered into the dust bag  12  which serves to trap the suspended dirt, dust and other particles inside while allowing the now clean air to pass freely through to the suction fan  34 , a final filtration cartridge (not shown) and ultimately to the environment through the exhaust port (not shown). 
   As best shown in  FIGS. 2   a  and  2   b , the nozzle assembly  14  includes a hollow stub shaft  52  at one side thereof. This stub shaft  52  is received and nests in a cooperating groove  54  provided in the canister assembly  16 . For clarity of illustration both portions of the canister assembly  16  are shown in  FIG. 3   a . Only the rear portion is shown in  FIGS. 3   b ,  3   c  and  4 . The two portions of the canister assembly  16  mate along the centerline of the groove  54  to aid in the overall assembly of the vacuum cleaner  10 . While not shown, it should be appreciated that a similar structural configuration may be provided on the other side of the vacuum cleaner  10  to provide the same function. The two stub shafts are aligned to provide a single axis about which the nozzle assembly  14  pivots relative to the canister assembly  16  during vacuum cleaner operation. 
   As further illustrated, a biaser, in the form of a torsion spring  56 , is partially received in the stub shaft  52 . More specifically, the coiled portion  58  of the spring  56  is positioned in the stub shaft  52 . A first end  60  of the spring is received in an aperture  62  in the metal reinforcing plate  64  of the nozzle assembly  14 . A second end  66  of the spring  56  extends through a slot  68  in the wall of the stub shaft  52  downwardly into a channel  70  formed by a box rib  72  on the wall  74  of the canister assembly  16 . When the canister assembly  16  is in the full down position (see  FIG. 3   a ) forming an included angle with the nozzle assembly  14  of approximately 170°-178°, the second end  66  of the spring  56  projects downwardly just inside the forward edge  76  of the groove  68  and provides the necessary spring force to urge the nozzle assembly downwardly into engagement with the surface being cleaned. 
   As the control handle  18  and canister assembly  16  are pivoted upwardly to an included working angle of approximately 135° with the nozzle assembly  14 , (i.e. into an angular orientation commonly employed during use of the vacuum cleaner by the operator) shown in  FIG. 3   b , the forward wall  78  of the box rib  72  partially winds the torsion spring  56 . This further increases the downforce on the forward end of the nozzle assembly  14  so as to better insure that the nozzle assembly  14  stays down in engagement with the ground as the vacuum cleaner is moved back-and-forth by means of the handle. 
   As the handle  18  and canister assembly  16  are pivoted still further with respect to the nozzle assembly  14  toward the upright position, further winding of the torsion spring  56  occurs (see  FIG. 3   c ). It should be appreciated that the slot  68  cut in the stub shaft  52  provides sufficient clearance to allow free passage of the end  66  of the spring  56  into the channel  70  in all the various angular orientations that the canister assembly  16  may assume with the nozzle assembly  14 . Thus the spring  56  provides in all operating positions between about 1.2 and about 3.2 and more typically between about 2.0 and about 2.4 lbs/sq. in. of preload. This converts to between about 0.2 and 3.0 lbs/sq. in. of downforce on the forward end of the nozzle assembly  14 . Thus, when the canister assembly  16  is positioned at about a 135° working angle with the nozzle assembly  14  (see  FIG. 3   b ), the spring may provide a downforce of between about 0.8 and about 1.6 lbs/sq. in. and more typically about 1.2 lbs/sq. in. on the forward end of the nozzle assembly  14 . These specific ranges are, of course, only mentioned to be illustrative of the invention and are not to be considered restrictive. 
   Numerous benefits result from employing the concepts of the present invention. The downforce the spring  56  exerts on the nozzle assembly  14  serves a dual function. First, it resists any tendency of the nozzle assembly  14  to be lifted from the floor being cleaned as the vacuum cleaner  10  is manipulated or pushed and pulled back-and-forth by the operator. As a consequence, the agitators  38   a  and  38   b  are better maintained in contact with the floor. This promotes more efficient and effective cleaning. Second, it has a tendency to dampen any vibration resulting from the engagement of the agitators  38   a ,  38   b  or the brushes, beater bars or other cleaning structures carried thereon with the surface being cleaned. This advantageously reduces or eliminates this operator annoyance which may otherwise become very pronounced when the vacuum cleaner is operated on surfaces having particular physical characteristics. Further, it should be appreciated that these benefits are also provided and are even more pronounced when the vacuum cleaner is constructed from lightweight materials. Such vacuum cleaners are user friendly since they are easier and more convenient to move and manipulate. 
   The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. For example, while a vacuum cleaner with dual agitators is illustrated, the invention is equally applicable to a vacuum cleaner with one agitator or more than two agitators. The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.