Patent Publication Number: US-2010109410-A1

Title: Patient Chair With Locking Assembly

Description:
TECHNICAL FIELD  
     The present invention relates generally to chairs for supporting a patient during examinations and treatments, and more particularly to a chair for use in a dental operatory. 
     BACKGROUND  
     Conventional dental operatories generally include an articulating dental chair for supporting a patient in a variety of positions to facilitate the performance of dental procedures and operations. For example, dental chairs are generally adapted to be raised and lowered relative to a floor surface, and to be moved between a first orientation where a back cushion is inclined relative to a seat cushion to support the patient in a seated position, and a second orientation where the seat cushion is reclined to support the patient in a generally supine position. 
     In some dental chairs, the seat cushion is supported by a chair frame and the back cushion is coupled to an upright support that moves relative to the chair frame along a predetermined path or track (i.e., the support does more than merely pivot with respect to the chair frame). This upright support is sometimes referred to as a “carriage.” A lower portion of the carriage is typically received between sidewalls of the chair frame. The carriage slides relative to the chair frame between the sidewalls and along the predetermined path to move the dental chair between the first and second orientations mentioned above. 
     One of the challenges associated with this type of dental chair relates to coupling the carriage to the chair frame. The carriage should be coupled (i.e., connected) to the chair frame in a manner that allows movement between the first and second orientations without a significant amount of “slop” or “play” between the components. In other words, the carriage should remain relative stable relative to the chair frame as the seatback is moved through its range of motion (both from the first orientation to the second orientation and vice-versa). 
     To address this concern, manufacturers may design the carriage, chair frame, and various other associated components to have relatively tight tolerances. For example, the lower portion of the carriage may be received between the sidewalls of the chair frame with little clearance. However, designing components with relatively tight tolerances increases the potential for poor fits or mismatches between the components. 
     Therefore, a dental chair that provides an improved fit between a carriage and a chair frame without requiring relatively small tolerances is highly desirable. 
     SUMMARY  
     A chair for supporting a patient during examinations or treatments is described below. The chair is particularly suited for use in a dental operatory, although the invention is not so limited. 
     In one embodiment, the chair generally comprises a base, a chair frame supported by the base, and a seatback support (or “carriage”) coupled to the chair frame. The seatback support is slidably movable relative to the chair frame. To provide a “close fit” or proper connection between components, a locking assembly is configured to apply a clamping force between the seatback support and the chair frame. 
     In another embodiment, the chair frame includes first and second sidewalls. The seatback support has a lower portion received between the first and second sidewalls, and the locking assembly is associated with one of the first or second sidewalls. The locking assembly includes an engagement member coupled to the lower portion of the seatback support, a clamp plate facing an outer surface of the associated first or second sidewall, and a fastener having a head portion retained against the clamp plate and a shaft portion extending through the clamp plate and first or second sidewall. The shaft portion has threads for engaging the engagement member. 
     In yet another aspect or embodiment, the chair further includes a drive mechanism supported by the chair frame and coupled to the seatback support. The drive mechanism is configured to slidably move the seatback support relative to the chair frame. In some embodiments, the drive mechanism is a one-way hydraulic cylinder configured to move the seatback support from a reclined position to an upright position relative to the chair frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a chair according to one embodiment for supporting a patient during examinations or treatments. 
         FIG. 2  is a side elevational view, partially in cross-section, of the chair shown in  FIG. 1 . 
         FIG. 3  is another perspective view of the chair shown in  FIG. 1  with various components removed for clarity. 
         FIG. 4  is an exploded perspective view of the components of the chair shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION  
       FIG. 1  shows one embodiment of a chair  2  for supporting a patient during medical examinations, treatments, or the like. The type of examinations and treatments may vary such that chair  2  may be used by many different types of practitioners. For example, chair  2  may be used as part of a dental operatory to support a patient during dental procedures. To this end (and in a manner not shown herein), chair  2  may be used in combination with any of the components typically associated with a dental operatory, such as: a dental delivery unit or tray that supports various instruments and tools, a cuspidor that permits patients to expel the contents of their mouths, an adjustable lamphead that illuminates the treatment area, and various other devices useful for the performance of dental procedures. 
     Chair  2  generally comprises base  4 , a lift arm  6  extending upwardly from base  4 , and a seat assembly  8  supported by lift arm  6 . Lift arm  6  raises and lowers seat assembly  6  relative to base  4 . A seatback support  10  (referred to as a “carriage”) extends generally upwardly from seat assembly  8  for supporting a seatback frame  12  ( FIG. 2 ) and a back cushion  14  mounted to seatback frame  12 . As will be described in greater detail below, chair  2  can move from the generally upright position/orientation shown in  FIG. 1  to a generally reclined position/orientation. 
     In one embodiment, seat assembly  8  includes a chair frame  20  mounted to lift arm  6  by a seat mount assembly  21 , a casing assembly  22  mounted to chair frame  20 , and a seat cushion  24  positioned over chair frame  20  and casing assembly  22 .  FIGS. 2 and 3  illustrate chair frame  20  and seatback support  10  in further detail. Chair frame  20  supports a drive mechanism  26  between first and second sidewalls  28 ,  30 . Drive mechanism  26  is configured to slide seatback support  10  relative to chair frame  20  along a predetermined path to move chair  2  between a generally upright position ( FIG. 2 ; corresponding to a seated position of the patient) and a generally reclined position (not shown; corresponding to a generally supine position of the patient). To this end, seatback support  10  includes a lower portion  34  received between the first and second sidewalls  28 ,  30 . Drive mechanism  26  is connected to a support shaft  36  extending through lower portion  34 . More specifically, drive mechanism  26  includes a piston rod  38  connected to support shaft  36  for applying a linear force to lower portion  34  of seatback support  10 . When this force is applied, lower portion  34  is guided through an arcuate path defined by arcuate tracks  40  in the first and second sidewalls  28 ,  30 . 
       FIG. 4  illustrates the components that guide seatback support  10  through this motion in further detail. As shown in  FIG. 4 , a first guide shaft  46  extends through lower portion  34  of seatback support  10  behind (i.e., proximal of) support shaft  36 . First guide shaft  46  includes a first end portion  48  that extends through arcuate track  40  of first sidewall  28  and a second end portion (not shown) that extends through arcuate track  40  of second sidewall  30 . Second and third guide shafts  54 ,  56  are substantially aligned along a common axis and extend partially through lower portion  34  of seatback support  10  in front of (i.e., distal of) support shaft  36 . Second guide shaft  54  includes an end portion  58  extending through arcuate track  40  of first sidewall  28 , and third guide shaft  56  includes an end portion  60  extending through arcuate track  40  of second sidewall  30 . Bushings  62  and/or bearings (not shown) may be provided on each of the end portions  48 ,  58 ,  60  to facilitate movement through the associated arcuate track  40 . It will be appreciated, however, that various other structure may alternatively be used to facilitate movement of the respective portions of guide shafts  46 ,  54 ,  56  through the arcuate tracks  40 . As can be appreciated, first, second, and third guide shafts  46 ,  54 ,  56  cooperate with arcuate tracks  40  to translate the linear forces applied by piston rod  38  to seatback support  10  into arcuate motion. 
     The drive mechanism  26  shown in  FIG. 4  includes a one-way hydraulic cylinder  68  positioned within a housing  70  (referred to as a “trunnion”) pivotally mounted to chair frame  20 . Piston rod  38  thus applies force in a single direction. In the embodiment shown, piston rod  38  applies a pushing force to move lower portion  34  of seatback support  10  toward a rearward end  72  of each arcuate track  40 . The rearward position shown in  FIGS. 2-4  corresponds to the generally upright position of chair  2 . 
     When the force of drive mechanism  26  is released, one or more return springs  76  pull support shaft  36  and lower portion  34  of seatback support  10  toward a forward end  78  of each arcuate track  40 . Again, the first, second, and third guide shafts  46 ,  54 ,  56  cooperate with arcuate tracks  40  to translate the applied forces into arcuate motion. Those skilled in the art will appreciate that this arrangement is merely one example of how seatback support  10  may slide relative to chair frame  20 . Indeed, chair  2  may alternatively include a two-way hydraulic cylinder, a mechanical linear actuator, or any other type of drive mechanism  26  for moving seatback support  10  relative to chair frame  20 . 
     Now referring to  FIGS. 3 and 4 , chair  2  further includes a locking assembly  80  associated with first sidewall  28 . Locking assembly  80  includes an engagement shaft  82  coupled to seatback support  10 , a clamp plate  84  facing an outer surface  86  of first sidewall  28 , and a fastener  88 . Engagement shaft  82  is substantially aligned along the same axis as support shaft  36  and includes a bore  90  for receiving an end portion  94  of support shaft  36  at a first end  92  of engagement shaft  82 . First end  92  is coupled to both support shaft  36  and lower portion  34  of seatback support  10  by a fastener  100  extending through holes  102 ,  104 . At a second end  108  of engagement shaft  82 , bore  90  is threaded and configured to receive a shaft portion  110  of fastener  88 . More specifically, fastener  88  includes a head portion  112  retained against clamp plate  84  and a shaft portion  110  that extends through clamp plate  84  and first sidewall  28  to engage bore  90 . Fastener  88  may be, for example, a flat head screw. 
     In one embodiment, clamp plate  84  further includes a first clearance hole  120  substantially aligned with the axis of first guide shaft  46  and a second clearance hole  122  substantially aligned with the axis of second and third guide shafts  54 ,  56 . The end portions  48 ,  58  of the first and second guide shafts  46 ,  54  extend through the respective clearance holes  120 , 122  when locking assembly  80  is installed. Various spacing components may be provided over first and second guide shafts  46 ,  54  between first sidewall  28  and clamp plate  84 . For example, as shown in  FIG. 4 , a wave spring washer  128 , a flat steel washer  130 , and a Delrin washer  132  may be provided over each guide shaft  46 ,  54 ,  56  between clamp plate  84  and outer surface  86  of first sidewall  28 . 
     To assemble chair  2 , seatback support  10  is positioned between the first and second sidewalls  28 ,  30  of chair frame  20  and guide shafts  46 ,  54 ,  56  are positioned with their end portions  48 ,  58 ,  60  in the associated arcuate track  40 . At this point, there may be a small amount of “play” between seatback support  10  and chair frame  20 . To provide a more stable arrangement, clamp plate  84  is positioned with clearance holes  120 ,  122  over the respective end portions  48 ,  58  of first and second guide shafts  46 ,  54 . Shaft portion  110  of fastener  88  is inserted through a central hole  136  in clamp plate  84  and into bore  90  of engagement shaft  82 . Fastener  88  is then tightened (i.e., rotated) to engage shaft portion  110  with the threads of bore  90  thereby pulling seatback support  10  toward first sidewall  28 . Because head portion  112  of fastener  88  is retained against the clamp plate  84 , locking assembly  80  applies a clamping force between seatback support  10  and first sidewall  28 . This clamping force maintains a relatively stable connection between seatback support  10  and chair frame  20  so as to eliminate “slop” during the movement of seatback support  10  between the generally upright position and the generally reclined position. 
     As can be appreciated, locking assembly  80  reduces or eliminates the need to design the seatback support  10  and chair frame  20  with relatively tight tolerances. There may be a fair amount of play when the components are first assembled, but the play is eliminated when locking assembly  80  is tightened. This may be a one-time step performed when chair  2  is first assembled. Casing assembly  22  ( FIG. 1 ) and/or seat cushion  24  may be assembled over locking assembly  80  after the initial adjustments are made to conceal locking assembly  80 . Alternatively, locking assembly  80  may be adjusted as needed whenever seatback support  10  begins show signs of “slop.” 
     While the invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, engagement shaft  82  may be replaced with any suitable structural component coupled to lower portion  34  of seatback support  10  and configured engage fastener  88 . Indeed, it will be appreciated that other components of locking assembly  80  described with specificity above may be replaced with other structural elements capable of performing similar functions. Additionally, although chair  2  only includes a single locking assembly  80 , an additional locking assembly (not shown) may be associated with second sidewall  30  if desired. 
     The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of the general inventive concept.