Abstract:
A pivot assembly for a swiveling chair is provided. The pivot assembly includes an elongated rod received in a tubular element, the elongated rod being capable to pivot by the intermediary of bearing assemblies such as to allow the chair to swivel. Each bearing assembly includes two segments mechanically engaged with one another. Each bearing assembly is responsive to pressure tending to urge the segments toward one another such as to close itself on the elongated rod and thus reduce or eliminate any clearance that may develop between the elongated rod and the bearing assembly. This arrangement is useful because it eliminates or at least it reduces free play that may develop in the components of the pivot assembly over time.

Description:
FIELD OF THE INVENTION 
     The present invention relates to of the art of manufacturing chairs and, more particularly, to a novel pivot assembly for swiveling chairs. The pivot assembly is characterized by its ability to maintain tight tolerances between its component parts during its useful life to prevent undesirable free play felt by the occupant of the chair when the latter shifts the position of his body while being seated. 
     BACKGROUND OF THE INVENTION 
     A typical swiveling chair includes a body supporting structure that is mounted on a chair base by a pivot assembly. Many different pivot assembly arrangements have been developed in the past to suit a wide variety of applications. One type of pivot assembly that is fairly common comprises an elongated rod that extends generally upright, depending from the body supporting structure. The elongated rod is received in a tubular element that is secured to the chair base. Bearings between the elongated rod and the tubular element allow the swiveling motions to take place. Normally, two separate bearing assemblies are used to connect the elongated rod to the tubular element. The two bearing assemblies are mounted in spaced apart relationship on the elongated rod. 
     It is well known that overtime the clearances between the various components of the pivot assembly will progressively increase. This occurs as a result of normal wear. This increase in clearances will result in an undesirable free play in the pivot assembly that can be distinctly felt by the user, particularly as a result of body shifts. For example, when the body of the user leans forward or leans backwards the center of gravity crosses the imaginary vertical plane containing the swiveling axis and makes this free play particularly noticeable. 
     To overcome, this problem, it is known to provide the pivot assembly with an adjustable cushion designed to reduce the undesirable free play. This adjustable cushion is in the form of a polymeric sleeve that is placed within the tubular element and surrounds the elongated rod. Adjustment screws are placed on the tubular element to urge the polymeric sleeve towards the elongated rod such as to eliminate the free play. The difficulty of this approach is the requirement from the user to make periodic adjustments. Also, once an adjustment has been made the polymeric sleeve will be able to eliminate or reduce the free play usually over a fairly short period of time, such as a couple of weeks. After this period of time has elapsed, the free play will progressively reappear and the user will be required to perform the adjustment again. 
     Against this background, it clearly appears that there is a need in the industry to provide a pivot assembly that has the ability to maintain tight tolerances between its component parts over long time periods and that does not require frequent periodic adjustments. 
     SUMMARY OF THE INVENTION 
     In one aspect the present invention provides a pivot assembly for a swiveling chair, the pivot assembly being suitable for supporting a body supporting structure of the chair on a chair base and allow the body supporting structure to swivel with relation to the chair base. The pivot assembly comprises a first pivot assembly component for connection to the body supporting structure and a second pivot assembly component for connection to the chair base. One of the first and second pivot assembly components including an elongated rod oriented generally upright. 
     A bearing assembly is mounted between the first and the second pivot assembly components to allow the pivot assembly components to swivel one with relation to the other. The bearing assembly defines an aperture that receives the elongated rod. The bearing assembly is responsive to pressure applied downwardly on the pivot assembly to tend to close the aperture on the elongated rod. 
     The downward pressure applied on the bearing assembly can originate from different sources. In one possible nonlimiting example of implementation, the downward pressure is a combination of two factors, the first factor being the weight of the body of the occupant when seated in the body supporting structure, while the second factor is a resilient element that urges the pivot assembly downwards. It should be appreciated that in this specific nonlimiting example of implementation, the resilient element is optional and it can be omitted without departing from the spirit of the invention. Under a possible variant where no resilient element is present, the pivot assembly relies solely on the weight of the body of the occupant to generate the downward pressure necessary to tend to close the aperture in the bearing assembly around the elongated rod. Yet, another possibility is to provide a large resilient element that alone, without relying on the body weight of the occupant, could generate the downward pressure sufficient to tend to close the aperture of the bearing assembly on the elongated rod in a manner to reduce or eliminate clearances. 
     Having regards to the above, it should be appreciated that the expression “downwards pressure” in this specification is not limited to any particular external influence or a combination of external influences that generate the downward pressure acting on the pivot assembly. The expression “downward pressure” is intended to encompass all possible sources or combination of such sources of downward force acting on the pivot assembly as long as the resulting magnitude is sufficient to tend to close the aperture of the bearing assembly on the elongated rod. 
     The advantage of this pivot assembly in accordance with this invention is its ability to maintain tight tolerances primary between the elongated rod and the bearing assembly. As a result, less frequent adjustments are necessary to compensate for free play by comparison to prior art devices. 
     In a specific nonlimiting example of implementation, the first pivot assembly component is the elongated rod while the second pivot assembly component is a tubular element that receives the elongated rod. The bearing assembly includes a first segment and a second segment concentrically mounted on the elongated rod. The first segment of the bearing assembly includes a downward tapering recess formed on the second segment. The first segment includes a slot that extends along the elongated rod. Functionally, under this nonlimiting example of implementation, the first segment behaves as a slotted ring and it can be progressively tightened on the elongated rod in response to radial force applied on the first segment. This radial force is generated as a result of the tapering configuration of the mating surfaces of the first and of the second segments, when downward pressure is applied on the pivot assembly. implementation, the pivot assembly includes a second bearing assembly that is mounted on the elongated rod and it is in a spaced apart relationship with relation to the first bearing assembly. The second bearing assembly functions in a similar manner as the first bearing assembly with one notable exception. This exception is that the mating surfaces between the first and the second segments of the second bearing assembly are oriented in such a way that they taper upwardly, in other words opposite the direction of taper of the mating surfaces of the first and the second segments of the first bearing assembly. 
     Under a different aspect, the present invention provides a pivot assembly for a swiveling chair, the pivot assembly being suitable for supporting a body supporting structure of the chair on a chair base and allowing the body supporting structure to swivel with relation to the chair base. The pivot assembly comprises a first pivot assembly component for connection to the body supporting structure and a second pivot assembly component for connection to the chair base. One of the first and second pivot assembly components includes an elongated rod oriented generally upright. A bearing assembly is mounted between the first and second pivot assembly components to allow the pivot assembly components to swivel one with relation to the other. The bearing assembly defines an aperture that receives the elongated rod. The bearing assembly includes a first segment and a second segment that are mechanically engaged and operative to pivot one with relation to another when the pivot assembly swivels. The bearing assembly is responsive to pressure urging the segments toward one another to tend to close the aperture on the elongated rod. 
     The pressure urging the segments of the bearing assembly toward one another can come from one or more sources, such as the body weight of the occupant of the chair and/or a resilient element in the pivot assembly operative to urge the segments toward one another. 
     The present invention also extends to a swiveling chair including the pivot assembly described above. 
     In a different aspect the invention provides a pivot assembly for a swiveling chair, the pivot assembly being suitable for supporting the body supporting structure of the chair on a chair base and allowing the body supporting structure to swivel with relation to the chair base. The pivot assembly comprises a first pivot assembly component for connection to the body supporting structure and a second pivot assembly component for connection to the chair base, one of the first and second pivot assembly components including an elongated rod oriented generally upright. A bearing assembly is mounted between the first and the second pivot assembly components. The bearing assembly allows the pivot assembly components to swivel one relative to the other. The bearing assembly includes a first segment and a second segments, the first segment including a tapered projection and being concentrically mounted on the elongated rod. The first segment is secured on the elongated rod against movement on the elongated rod along a direction parallel to the elongated rod and a direction transverse to the elongated rod. The second segment includes a tapered recess receiving the tapered projection. The first and second segments are in mechanical engagement and operative to pivot one with relation to the other when the pivot assembly swivels. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a rocking and a swiveling chair incorporating the pivot assembly constructed according to the principles of the present invention. In FIG. 1, only the structure of the chair is shown, the upholstery being removed for purposes of clarity; 
     FIG. 2 is a perspective view of the mechanism allowing the chair of FIG. 1 to rock and to swivel; 
     FIG. 3 is a perspective exploded view of the pivot assembly of the chair shown in FIG. 1; 
     FIG. 4 is a perspective view of the second segment of the first bearing assembly of the pivot assembly in accordance with the invention; 
     FIG. 5 is d side elevational view of the second segment shown in FIG. 4; 
     FIG. 6 is a bottom plan view of the second segment shown in FIG. 4; 
     FIG. 7 is a cross sectional view taken along lines  7 — 7  in FIG. 6; 
     FIG. 8 is a cross sectional view taken along lines  8 — 8  in FIG. 6; 
     FIG. 9 is a perspective view of the first segment of the first bearing assembly of the pivot assembly in accordance with the invention; 
     FIG. 10 is a top plan view of the first segment depicted in FIG. 9; 
     FIG. 11 is a side elevational view of the first segment depicted in FIG. 9; 
     FIG. 12 is a cross sectional view taken along lines  12 — 12  in FIG. 10; 
     FIG. 13 is a perspective view of the second segment of the second bearing assembly of the pivot assembly in accordance with the invention; 
     FIG. 14 is a side elevational view of the second segment depicted in FIG. 13; 
     FIG. 15 is a bottom plan view of the second segment depicted in FIG. 13; 
     FIG. 16 is a cross sectional view of the second segment taken along lines  16 — 16  in FIG. 15; 
     FIG. 17 is a perspective view of the first segment of the second bearing assembly of the pivot assembly in accordance with the invention; 
     FIG. 18 is a top plan view of the first segment depicted in FIG. 17; 
     FIG. 19 is a cross sectional view taken along lines  19 — 19  in FIG. 18; 
     FIG. 20 is a cross sectional view taken along lines  20 — 20  in FIG. 18; 
     FIG. 20 a  is a fragmentary side elevational view of an elongated rod; 
     FIG. 21 is a top plan view of the pivot assembly in accordance with the invention; 
     FIG. 22 is a cross sectional view taken along lines  21 — 21  in FIG. 21; 
     FIG. 23 is an enlarged view of a first bearing assembly of the pivot assembly shown in FIG. 22; 
     FIG. 24 is an enlarged view of a second bearing assembly of the pivot assembly shown in FIG.  22 . 
     FIG. 25 is a side elevational view of the elongated rod of the pivot assembly according to a variant. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 of the drawings illustrates a chair designated by the reference numeral  20  that embodies the principles of the present invention. The chair  20  can be broken down into three main components namely a body supporting structure  22 , a chair base  24  and a pivot assembly  26  that connects the body supporting structure  22  to the chair base  24 . 
     The body supporting structure  22  comprises two main components namely a seat portion  28  and a backrest  30 . The chair base  24  comprises a circular member of sufficient size to adequately support the chair  20  on the floor, although this is only a question of design since a wide variety of chair bases can be used here without departing from the spirit of the invention. 
     The pivot assembly  26  is depicted in greater detail in FIG.  2 . In the example of implementation of the invention illustrated in the drawings, the pivot assembly  26  allows the body supporting structure  22  to swivel about a generally vertical axis  32 . The pivot assembly  26  is also combined to a rocking mechanism  34  that allows the body supporting structure  22  to rock back and forth. It should be noted that the rocking capability of the chair is merely optional and the pivot assembly  26  according to the invention can be used in chairs that do not rock. 
     FIG. 3 provides an exploded view of the pivot assembly  26 . The pivot assembly  26  comprises a tubular element  36  that includes near the lower extremity a flange  38  provided with apertures  40  to receive fasteners allowing to retain the tubular element  36  to the chair base  24 . This is one from of realization only as many other ways to mount the tubular element  36  to the chair base  24  can be used without departing from the spirit of the invention. The tubular element  36  receives an elongated rod  42  that can pivot about the swiveling axis  32  through the intermediary of two bearing assemblies, namely a first bearing assembly  44  and a second bearing assembly  46 . The bearing assemblies  44 ,  46  are mounted on the elongated rod  42  in a spaced apart relationship such as to support portions of the elongated rod  42  that register with the upper end and with the lower end of the tubular element  36 , respectively. 
     The first bearing assembly  44  includes two components namely a first segment  48  and a second segment  50 . The structure of the second segment  50  is depicted in FIGS. 4,  5 ,  6 ,  7  and  8 . The second segment  50  includes an annular body with a radially projecting flange  52  from which depends a cylindrical element  53 . The cylindrical element  53  carries a plurality of regularly spaced and radially projecting ribs  54 . The second segment  50  defines a centrally located circular bore  56  designed to accommodate the elongated rod  42 . Referring now to FIGS. 7 and 8 that show cross-sectional views of the second segment  50 , it will be apparent that the second segment  50  defines immediately above the circular bore  56  a tapering recess  58 . The recess  58  tapers downwardly. 
     The second segment  50  is made from plastic material and it is designed to be forcibly inserted into the upper extremity of the tubular member  36 . Accordingly, the diameter of the array of ribs  54  should slightly exceed the internal diameter of the tubular member  36 . During the installation, the second segment  50  is applied with pressure against the tubular element  36  to cause the ribs  54  to compress or distort and frictionally engage the inner wall of the tubular element  36 . 
     The second segment  50  is designed to receive the first segment  48  that is illustrated in greater detail in FIGS. 9,  10 ,  11  and  12 . The first segment  48  comprises an annular tapering body in the form of a truncated cone. In particular, the first segment  48  comprises an outer tapering wall  60  whose geometrical configuration matches the configuration of the recess  58  in the second segment  50 . Accordingly, the first segment  48  is capable to matingly engage the second segment  50  and rotate therein. The first segment  48  includes a central bore  62  defined by an array of radially inwardly projecting fingers  64 . In a possible variant, the internal wall defining the bore  62  may be smooth and continuous, rather than including fingers  64 . 
     The first segment  48  includes a slot  66  that extends completely from one extremity of the first segment  48  to the other extremity thereof and also extends transversely from the outer tapering wall  60  to the internal aperture  62 . The slot  66  is oriented in such manner that it extends along the elongated rod  42 . The dimensions of the first segment  48  are such the diameter of the bore  62  is slightly less than the diameter of the rod  42 . To fit the first segment  48  on the rod  42  it suffices to open up the first segment  48  (this movement is allowed by the slot  66 ) against the resiliency of the first segment  48  such as to slip the first segment  48  on the elongated rod  42 . 
     In use, the first segment  48  is received in the second segment  50 . The respective bores  56 ,  62  acquire a condition of alignment and jointly define an aperture of the bearing assembly  44  that can receive the elongated rod  42 . The first segment  48  behaves as a slotted ring that, in response to radial pressure applied against the wall  60  tends to close, by virtue of the slot  66 , the aperture of the bearing assembly  44 . This causes the clearance between the ribs  64  and the elongated rod  42  to diminish and to be entirely eliminated when the ribs  64  engage the surface of the elongated rod  42 . 
     The first segment  48  also comprises a pair of projections  68  that originate from the base of the inverted truncated conical structure. The projections  68  are received in a horizontal bar  10  (refer to FIGS.  3  and  23 ) from which depends the elongated rod  42 . The projections  68  are received in corresponding recesses or apertures  69  formed on the horizontal bar  70  and are primarily designed to lock the first segment  48  on the elongated rod  42  against rotation. In other words, this arrangement causes the first segment  48  to pivot in the second segment  50  when the elongated rod  42  turns. 
     The first segment  48  is made of any suitable plastics material that resists abrasion and is also sufficiently solid to withstand the pressures applied on it during use. Nylon has been found to be suitable for this purpose. 
     Referring back to FIG. 3, the second bearing assembly  46  comprises a first segment  80  and a second segment  82  that are matingly received into one another. The structure of the second segment  82  is illustrated in greater detail in FIGS. 13,  14 ,  15 , and  16 . The structure of the second segment  82  is very similar to the structure of the second segment  50  with the exception that the body of the second segment  82  is slightly longer, while their external transverse dimensions are about the same. More particularly, the second segment  82  comprises a radially projecting flange  84  from which extends upwardly a cylindrical body  86 . From the cylindrical body  86  project radially an array of regularly spaced ribs  88  whose purpose is to frictionally engage the inner wall at the lower end of the tubular element  36  to retain the second segment  82  in the tubular element  36 . The cylindrical body  86  defines at its upper end a circular bore  90  designed to receive the elongated rod  42 . Internally, as it will be apparent from FIG. 16 the second segment  82  defines an upwardly tapering recess  92 . 
     FIGS. 17,  18 ,  19  and  20  illustrate the structure of the first segment  80 . Functionally speaking, the first segment  80  is similar to the first segment  48  described earlier in that it is capable of closing the aperture defined by the bearing assembly  46  around the elongated rod  42  in order to reduce or eliminate clearances. More particularly, the first segment  80  is in the shape of a truncated conical body comprising an outer tapering wall  100 . Internally, as best shown at FIGS. 19 and 20, the first segment  80  includes a generally cylindrical void  102 . At the base of this void is provided a generally cylindrical projection  104  that is of a lesser diameter than the diameter of the cylindrical void  102 . This arrangement creates at the base of the void  102  an annular space  106  whose continuity is interrupted only by a key  108 . The key  108 , as shown at FIG. 18 approximates the shape of a rectangular body. The purpose of the key  108  as it will be described later in greater detail is to lock the first segment  80  on the elongated rod  42  such as to prevent the two components from pivoting one with respect to the other. 
     The cylindrical projection  104  defines a cavity  103  that includes a central bore  110  establishing a passageway between the cavity  103  and of the cylindrical void  102 . The purpose of the cavity  103 , as it will be described in greater detail later is to receive a coil spring to maintain the first and the second segment of the bearing assembly  46  pressed one against the other. The bore  110  is provided to receive a bolt for holding of the coil spring in place. 
     The first segment  80  also includes a slot  112  that extends along the elongated rod  42  creating a gap between the outer wall  100  and the internal bore  110 . As in the case of the first segment  48 , the slot  112  allows the first segment  80  to tighten the elongated rod when subjected to radial compression. 
     In use, the first segment  80  is received into the internal tapering recess  92  of the second segment  82 . When these two components are assembled, the bore  90  and the bore defined by the cylindrical void  102  are in a condition of alignment such as to create an aperture through which the elongated rod  42  can pass. The elongated rod  42  receives the first segment  80  at its lower end. The elongated rod  42  is hollow and it fits the annular space  106 . In addition, the lower end of the elongated rod  42  is provided with a notch  200  (shown in FIG. 20 a ) that is designed to accept the key  108 . In this fashion, the first segment  80  is prevented from rotating on the elongated rod  42 . Evidently, alternative ways of securing the first segment  80  on the elongated rod  42  can be considered without departing from the spirit of the invention. 
     The structure of the pivot assembly  26  in the fully assembled condition is shown at FIGS. 21,  22 ,  23  and  24 . Referring to FIG. 23, the first segment  48  of the bearing assembly  44  is received in the second segment  50 . The elongated rod  42  extends through the aligned bores of the first and second segments  48 ,  50 . FIG. 24 illustrates the bearing assembly  46  in greater detail. The elongated rod  42  is received into the first segment  80  that, in turn is received in the second segment  82 . A mechanical fastener  120  such as a bolt is inserted through the bore  110  and its threaded shank is engaged in the elongated rod  42 . A coil spring  122  is received in the cavity  103 . The coil spring  122  is maintained in a compressed condition in the cavity  103  by the head of the bolt  120 . 
     The relative dimensions between the elongated rod  42  and the first segment  80  are such as to create two gaps  123  and  125  that allow the first segment  80  to move axially on the elongated rod  42 . This movement is done against the resiliency of the coil spring  122 . This arrangement urges the segments of each bearing assembly  44 ,  46  toward one another. The consequence is to generate on the first segments  48 ,  80  a radial inwardly acting pressure by virtue of the tapering mating surfaces of the segments. As described earlier, such radial pressure causes the first segments  48 ,  80  to tend to close the apertures defined by the respective bearing assemblies, thus reducing or entirely eliminating clearances between the elongated rod  42  and the bearing assemblies  44 ,  46 . 
     This clearance reduction mechanism is enhanced at the level of the first bearing assembly  44  when a person sits in the chair. The body weight creates additional downward pressure on the bearing assembly  44  that causes the first segment  48  to close even further on the elongated rod  42 . 
     The downward pressure resulting from the weight of the occupant in the chair actually has the opposite effect on the bearing assembly  46  as it tends to unseat the first segment  80  from the second segment  82 . This movement is very limited in practice since the bearing assembly  44  prevents the elongated rod  42  to move downwardly, however, to some extent the segments of the bearing assembly  46  tend to separate from one another. This effect is counterbalanced by the coil spring  122  compensating any downward movement of the first segment  80 . Accordingly, the coil spring  122  acts to maintain a minimal amount of force on the first segment  80  against the second segment  82  that, in turn, produces at least some radial force on the first segment  80  tending to tighten it around the elongated rod  42 . 
     FIG. 25 illustrates a variant of the bearing assembly  44 . This bearing assembly, designated by the reference numeral  200  comprises a second segment  202  that is identical to the segment  50 . The bearing assembly  200  also comprises a first segment  204  that is formed integrally with the elongated rod  42 . This form of construction allows to lock the first segment  204  on the elongated rod  42  against any possibility of relative movement both in the axial direction and in the transverse direction. In one possible form of implementation, the first segments  204  and the elongated rod  42  are machined from a single piece of material. Alternatively, the first segment  204  can be manufactured separately from the elongated rod  42  and later affixed to the elongated rod such as to prevent movement between the two components. Adhesives, welding or any suitable mechanical fasteners can be used for this purpose. 
     It is intended that the present application covers the modifications and variations of this invention provided that they come within the scope of the appended claims and their equivalents.