Patent Publication Number: US-7914076-B2

Title: Device with a limit switch and trunnion

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to the following U.S. patent applications, each assigned to the Assignee of the present application: 
     U.S. patent application Ser. No. 12/262,887, filed Oct. 31, 2008; 
     U.S. patent application Serial No. 12/262,966, filed Oct. 31, 2008; 
     U.S. Design Application Serial No. 29/327,186, filed Oct. 31; 2008; and 
     U.S. Design Application Serial No. 29/327,189, filed Oct. 31, 2008. 
     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/position where a seatback is upright or inclined relative to a seat base to support the patient in a seated position, and a second orientation/position where the seatback 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. 
     Typically, once the first or second orientation/position is requested by a user, the motions associated with that orientation are performed until completion of the orientation. Often times, however, there may be an obstruction below the seatback that may interfere with the reclining seatback in the second orientation/position. The seatback is typically very heavy as it is meant to support a patient, and may cause pain or discomfort to the obstruction if the obstruction is another person. Despite the obstruction, the seatback typically continues to try to recline, causing additional pain or discomfort. 
     As an example, a dental hygienist may be sitting with his or her legs below the seatback, get distracted (e.g., assisting the dentist, preparing for the procedures, reviewing the charts, etc.), and not notice that the seatback is reclining until contact with the seatback. Upon contact by the seatback with the hygienist&#39;s legs, the seatback typically tries to continue to recline despite the dental hygienist&#39;s legs, often causing pain or discomfort. As such, the hygienist may be pinned down by the heavy seatback. 
     Thus, a need therefore exists in the art for a safer manner of reclining the seatback of the dental chair. 
     SUMMARY 
     The invention addresses these and other problems associated with the prior art by providing dental devices with cylinders, trunnions, and limit switches. The dental devices may be dental chairs. When the limit switch of the dental device is actuated, downward movement of the seat back may be stopped, often limiting further pain or discomfort to a user. 
     In some embodiments, the dental device may comprise a cylinder and a trunnion having a cavity and an outer surface. A portion of the cylinder is slidably mounted within the cavity of the trunnion and a portion of the cylinder protrudes out of the trunnion. The device may also include a limit switch coupled to the outer surface of the trunnion, where the limit switch contacts the cylinder. Separation of the limit switch and the cylinder causes actuation of the limit switch. The actuation of the limit switch stops a downward movement of the device. In other embodiments, the limit switch is coupled to the portion of the cylinder that protrudes out of the trunnion, and the limit switch contacts the trunnion. Separation of the limit switch and the trunnion, in these embodiments, causes actuation of the limit switch, stopping the downward movement of the device. 
     The invention also addresses problems associated with the prior art by providing a method of operating the dental device. The method includes providing a limit switch for the device that controls a downward movement of the device and initiating the movement of the device. The movement includes use of a cylinder and a trunnion. The method may also include detecting an obstruction, and in response to the detected obstruction, actuating the limit switch to stop the movement of the device. 
     These and other advantages and features, which characterize the invention, are set forth in the claims annexed hereto and forming a further part hereof. However, for a better understanding of the invention, and of the advantages and objectives attained through its use, reference should be made to the Drawings, and to the accompanying descriptive matter, in which there are described exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view, partially in cross-section, of one embodiment a dental chair in a generally raised position relative to a floor surface, with a seatback in a generally upright position relative to the chair frame. 
         FIG. 2  is a side elevational view of the dental chair of  FIG. 1  in a generally lowered position relative to the floor surface, with a seatback in a generally reclined position relative to the chair frame. 
         FIG. 3  is a partial top elevational view of the limit switch and drive assembly of the dental chair of  FIG. 1  in a non-contacting state. 
         FIG. 4  shows a side elevational view in partial cross-section of the limit switch of the dental chair of  FIG. 1  in a contacting state. 
         FIGS. 5A-5E  are partial side elevational views in partial cross-section of various components of the dental chair of  FIG. 1  illustrating the transition of the limit switch from a contacting state to a noncontacting state. 
         FIG. 6  is a flowchart of a routine for operating the dental chair of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Turning to the drawings, wherein like numbers denote like parts throughout the several views,  FIG. 1  shows one embodiment of a chair  2  for supporting a patient during 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, the 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), the 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. A dentist, dental hygienist, or other user may operate the chair  2 . 
     The chair  2  generally comprises a base  4 , a lift arm  6  extending upwardly from base  4 , and a seat assembly  8  supported by lift arm  6 . The lift arm  6  raises and lowers the seat assembly  8  relative to the base  4 . Lowering and raising the lift arm  6  is generally disclosed in U.S. patent application Ser. No. 12/262,887, filed on even date herewith by Hanus and entitled “DENTAL CHAIR WITH CANTILEVER FORWARD BASE” (MIDTF 467P2), the entire disclosure of which is incorporated by reference herein. 
     A seatback support  10  (referred to as a “carriage”) extends generally upwardly from the seat assembly  8  for supporting a seatback frame  12  and a back cushion  14  mounted to the seatback frame  12 . The seat assembly  8  includes a chair frame  20  pivotally mounted on a base structure  5 , which is attached to the lift arm  6 , a casing  22  mounted to the chair frame  20 , and a seat cushion  24  positioned over the chair frame  20  and the casing  22 . The seatback frame  12  may move downwardly by the downward movement of the seatback support  10  relative to the chair frame  20 . The seatback frame  12  may move upwardly by the upward movement of the seatback support  10  relative to the chair frame  20 . Indeed, the seatback frame  12  of the chair  2  can move from the generally upright orientation/position shown in  FIG. 1  to a generally reclined orientation/position shown in  FIG. 2 . 
     It is worth noting that movement of the seatback frame  12  may be independent from movement of the lift arm  6 , and vice versa. For example, the seatback frame  12  may be moved downwardly to a generally reclined position without raising or lowering the lift arm  6 . Indeed, the two separate motions may be performed consecutively or may be performed at about the same time. Moreover, the chair  2  may be preprogrammed using conventional techniques to achieve a certain setting, which may include movement of the seatback frame  12  alone, movement of the lift arm  6 , alone, or movement of both the seatback frame  12  and the lift arm  6 . Movement by both to accomplish the preprogrammed setting may be performed consecutively or at about the same time. 
     The chair  2  may have an input member (not shown) for moving the seatback frame  12  downwardly, a separate input member (not shown) for moving the seatback frame  12  upwardly, a separate input member (not shown) for lowering the lift arm  6 , a separate input member (not shown) for raising the lift arm  6 , and/or a separate input member (not shown) for a certain preprogrammed setting. The input member may be a button that may be depressed, a foot pedal that may be depressed, etc. Alternatively, the input member need not be depressed and may simply require contact. The user may select any of these positions by depressing the foot pedal (not shown), for example, until the desired position is achieved. However, when a setting is preprogrammed, the user may simply depress, for example, the preprogrammed input member to initiate the movement of the preprogrammed setting. The movement may occur without further action by the user, and the user may even be able to walk away from the chair  2  to tend to another matter. 
     Thus, the transition of the chair  2  to the manner shown in  FIG. 2  may be achieved by a user requesting the seatback frame  12  to be reclined and then by the user separately requesting the lift arm  6  to be lowered. Alternatively, the transition of the chair  2  to the positions shown in  FIG. 2  may be a preprogrammed setting. 
     To move the seatback frame  12 , the chair frame  20  supports a drive mechanism  26  between first sidewall  28  and second sidewall  30  ( FIG. 3 ). The drive mechanism  26  is configured to slide seatback support  10  relative to the chair frame  20  along a predetermined path to move the seatback frame  12  between a generally upright position ( FIG. 1 ; corresponding to a seated position of the patient) and a generally reclined position ( FIG. 2 ; corresponding to a generally supine position of the patient). The seatback support  10  also includes a lower portion  34  received between the first sidewall  28  and the second sidewall  30  ( FIG. 3 ). The drive mechanism  26  is connected to a support shaft  36  extending through the lower portion  34 . More specifically, the drive mechanism  26  includes a cylinder rod  38  connected to the support shaft  36  via rod end  39  for applying a linear force to the lower portion  34  of the seatback support  10 . When this force is applied, the lower portion  34  is guided through an arcuate path defined by arcuate tracks  40  in the first sidewall  28  and the second sidewall  30 . 
     To support this arcuate motion, the chair  2  may also contain a hydraulic fluid reservoir  41  and control circuitry  42 , both in the lift arm  6 . The control circuitry  42  may be in the form of a printed circuit board (PCB). The chair  2  may also include a solenoid  43 , which is associated with the drive mechanism  26  for the downward movement of the seatback frame  12 . Solenoid  43  opens or closes a valve  44 , with hydraulic fluid passing through the valve  44  when the valve  44  is opened. The chair  2  may additionally include a solenoid  45 , which is associated with the drive mechanism  26  for the upward movement of the seatback frame  12 . The solenoid  45  may also open or close the valve  44 . Indeed, the valve  44  may be placed between the solenoids  43  and  45 . Each of the solenoids  43 ,  45  may be configured to normally keep the valve  44  closed unless an electronic signal is sent to either of the solenoids  43 ,  45  to open the valve  44 . 
     Additional solenoids and valves (not shown) may be utilized for the downward movement of the lift arm  6  to lower the lift arm  6 . Similarly, separate solenoids and valves (not shown) may be utilized for the upward movement of the lift arm  6  to raise the lift arm  6 . Nonetheless, all of the solenoids and valves, including the solenoids  43 ,  45  and the valve  44 , may be within a manifold (not shown) in base  4 . A pump  47  may be present as illustrated in  FIG. 1  to support these movements and other movements. The pump  47  may be similar that disclosed in U.S. patent application Ser. No. 12/262,887, filed on even date herewith by Hanus and entitled “DENTAL CHAIR WITH CANTILEVER FORWARD BASE” (MIDTF 467P2), the entire disclosure of which is incorporated by reference herein. Additionally, these structures, and other structures, may be situated in locations that are different than those illustrated. 
     Turning to  FIG. 3 , which illustrates the components that guide the seatback support  10  through the arcuate motion and the drive mechanism  26  in more detail, a first guide shaft  46  extends through the lower portion  34  of the seatback support  10  behind (i.e., proximal of) the support shaft  36 . First guide shaft  46  includes a first end portion  48  that extends through the arcuate track  40  of the first sidewall  28  and a second end portion  49  that extends through the arcuate track  40  of the second sidewall  30 . Second and third guide shafts  54 ,  56  are substantially aligned along a common axis and extend partially through the lower portion  34  of the seatback support  10  in front of (i.e., distal of) the support shaft  36 . The second guide shaft  54  includes an end portion  58  extending through the arcuate track  40  of the first sidewall  28 , and the third guide shaft  56  includes an end portion  60  extending through the arcuate track  40  of the second sidewall  30 . Bushings (not shown) and/or bearings (not shown) may be provided on each of the end portions  48 ,  49 ,  58 ,  60  to facilitate movement through the associated arcuate track  40 . As can be appreciated, the first, second, and third guide shafts  46 ,  54 ,  56  cooperate with the arcuate tracks  40  to translate the linear forces applied by the cylinder rod  38  to the seatback support  10  into arcuate motion. 
     The drive mechanism  26  may include a one-way hydraulic cylinder  68  positioned within a cavity of a housing such as within a cavity of a trunnion  70 . A portion of the cylinder  68 , such as that closest to seatback support  10 , may protrude out of the trunnion  70 . The portion of the cylinder  68  that protrudes out of trunnion  70  may have an outside diameter of about 2¼ inches and an inside diameter of about 1¾ inches. The portion of the cylinder  68  within the cavity of the trunnion  70 , and that does not protrude, may have an inside diameter of about 1½ inches. The trunnion  70  may have an outside diameter of about 2¼ inches. The trunnion  70  may also be pivotally mounted to the chair frame  20 . Pivot axis  71  illustrates the general pivot point of the trunnion  70 . 
     Returning to  FIG. 1 , when a operator requests that the seatback frame  12  transition into a reclined position, for instance, after a patient sits in the chair  2 , the request may cause a signal to be sent to the control circuitry  42 , which in turn, may cause the control circuitry  42  to send a signal to the solenoid  43  to open the valve  44 . The control circuitry  42  may utilize transistor circuits to send electrical current to the solenoid  43 , which moves a spool to open the valve  44 . The opened valve  44  allows for hydraulic fluid (e.g., oil) to exit the cylinder  68  via the back hose  72  (e.g., a high pressure fitting). Upon exiting, the hydraulic fluid may flow to the manifold (not shown) containing the solenoid  43 , and then through the opened valve  44  into the hydraulic fluid reservoir  41 . Indeed, the hydraulic fluid may be under pressure, and the pressure may cause the exiting fluid to flow upwards into the hydraulic fluid reservoir  41 . Front hose  73  (e.g., a low pressure fitting) may serve as a catchall hose to transport into the hydraulic fluid reservoir  41  any hydraulic fluid that may seep through the internal structure of the cylinder  68 . 
     As the force of drive mechanism  26  is released by the exiting hydraulic fluid, one or more return springs  76  ( FIG. 3 ) pull the support shaft  36  and the lower portion  34  of seatback support  10  toward a forward end  78  of each of the arcuate tracks  40 . The first, second, and third guide shafts  46 ,  54 ,  56  ( FIG. 3 ) cooperate with the arcuate tracks  40  to translate the applied forces into arcuate motion. Via this process, the seatback  10  support is reclined relative to the chair frame  20 , with gravity being utilized to achieve the downward movement of the seatback  10 , and of the seatback frame  12 . Thus, the seatback frame  12  may transition from a generally upright position to a reclined position. 
     Once the reclined position is achieved, the control circuitry  42  stops signaling the solenoid  43 , and the solenoid  43  closes the valve  44 . When a reclined position is achieved by the seatback frame  12  may depend upon, for example, a preprogrammed setting, the length of time the request is held for by a user, etc. Nonetheless, additional hydraulic fluid may be prevented from exiting the cylinder  68  when the valve  44  is closed, and the reclined position may be maintained until a request for the generally upright position is received. 
     When a user requests that the seatback frame  12  transition into an upright position (e.g., with the user still sitting in the chair  2 ), the request may cause a signal to be sent to the control circuitry, which in turn, may cause the control circuitry  42  to send a signal to the solenoid  45  to open the valve  44 . The control circuitry  42  may utilize transistor circuits to send electrical current to the solenoid  45 , which moves a spool to open the valve  44 . As such, the hydraulic fluid may flow from the hydraulic fluid reservoir  41  to the manifold (not shown) containing the solenoid  45 , then through the opened valve  44 , up into back hose  72 , and into the cylinder  68 . As the hydraulic fluid may be under pressure, the pressure may cause the fluid to flow upwards into the back hose  72 . The front hose  73  may again serve as a catchall hose to transport seeping hydraulic fluid into the hydraulic fluid reservoir  41 . 
     As the hydraulic fluid enters the cylinder  68 , the hydraulic fluid acts on the cylinder rod  38 , which in turn applies a pushing force to move the lower portion  34  of the seatback support  10  toward a rearward end  79  of each arcuate track  40 . The first, second, and third guide shafts  46 ,  54 ,  56  ( FIG. 3 ) cooperate with the arcuate tracks  40  to translate the applied forces into arcuate motion. As such, the seatback  10  support of the chair  2  is upright relative to the chair frame  20 , and the seatback frame  12  transitions from the generally reclined position to the generally upright position. Once the generally upright position is achieved, the control circuitry  42  stops signaling the solenoid  45 , and the solenoid  45  closes the valve  44 . By closing the valve  44 , additional hydraulic fluid may be prevented from entering the cylinder  68 , and the upright position may be maintained until a request for the generally reclined position is received. 
     Next, the chair  2  may further include a locking assembly  80  ( FIG. 3 ) associated with first sidewall  28  as generally disclosed in U.S. patent application Ser. No. 12,262,966, filed on even date herewith by Hanus et al. and entitled “PATIENT CHAIR WITH LOCKING ASSEMBLY” (MIDTF 469P2), the entire disclosure of which is incorporated by reference herein. Moreover, the chair  2  also includes a limit switch  82  to override a request to transition the seatback frame  12  from a generally upright position to a generally reclined position. 
     Turning to the view of the limit switch  82  in  FIG. 4 , the limit switch  82  may be coupled to an outer surface of the trunnion  70  via a limit switch mounting member  89  such as a bracket. As illustrated, the limit switch  82  generally hovers parallel to horizontal outer surface  81  of the trunnion  70  because it is supported by the limit switch mounting member  89 . Member  89  may be coupled to a vertical outer surface of the trunnion  70 . However, in some embodiments, the limit switch  82  may be directly coupled to the horizontal outer surface  81 , instead of indirectly coupled to the horizontal outer surface  81  as illustrated in  FIG. 1  and  FIG. 4 . Coupled to the protruding portion of the cylinder  68 , via at least one attachment such as screws  83 , is a bracket  84 , and the limit switch  82  is operable to contact a contacting member such as the bracket  84 . The limit switch  82  may have a limit switch member such as a button  85  coupled to it, with the button  85  in contact with the bracket  84 . A contacting member may alternatively be a plate or other type of object with a surface that can contact the limit switch  82  and/or the limit switch member such as the button  85 . 
     A restraint member such as a fastener  86  (such as a pin, a screw, etc.) may be coupled to the trunnion  70  and operable to engage the bracket  84  (e.g., by passing through the bracket  84 ). The fastener  86  may reduce or inhibit rotational movement of the cylinder  68  within the trunnion  70 . The fastener  86  may be a low pressure fitting, and may also reduce or prevent interference with other components (e.g., interference of the front hose  73  on the cylinder  68  with the springs  76  in  FIG. 3 ). The fastener  86  may additionally facilitate contact between the limit switch  82  and the bracket  84  by maintaining a generally stable axis for the contact. 
     The limit switch  82  may start off in a contacting state, as illustrated in  FIG. 4 . The contacting state may be characterized by contact between the limit switch  82  or limit member thereof and the trunnion  70 . For example, the button  85  of the limit switch  82  is in contact with the bracket  84 . During the contacting state, the button  85  of the limit switch  82  may be depressed (e.g., completely depressed or partially depressed) by the contact with the bracket  84 . The springs  76  ( FIG. 3 ) may keep the button  85  in contact with the bracket  84 . Additionally, the limit switch  82  may be in communication with control circuitry  42  ( FIG. 1 ) via wiring  88 . The control circuitry  42  may be in communication with the solenoid  43 , and the solenoid  43  is operable to open and close the valve  44 , as discussed hereinabove. 
     Turning to  FIG. 2 , while transitioning the seatback support  10  relative to the chair frame  20  from the generally upright position to the generally reclined position, and thus transitioning the seatback frame  12  in response to a user request, one scenario that may occur is that the seatback frame  12  of the chair  2  comes in contact with an obstruction such as a box  92 . Alternatively, another scenario that may occur is that after transitioning the seatback support  10  relative to the chair frame  20  from the generally upright position to the generally reclined position, and thus transitioning the seatback frame  12 , the seatback frame  12  of the chair  2  may come in contact with the box  92  as the lift arm  6  is lowered in response to a user request. This latter scenario is depicted in  FIG. 2 . Nonetheless, under both scenarios the seatback frame  12  of the chair  2  may come in contact with the obstruction. 
     The obstruction may be an operator or a portion of the operator such as the legs of the operator. Alternatively, the obstruction may be an inanimate object such as the box  92  ( FIG. 2 ), a stool or chair for the operator to sit on, etc. Nonetheless, when the seatback frame  12  of the chair  2  contacts the obstruction, the limit switch  82  may transition from a contacting state in  FIG. 4  into a non-contacting state in  FIG. 3 . The non-contacting state actuates the limit switch  82 . Alternatively, the limit switch  82  may initially be in a non-contacting state, and contact with the obstruction causes the limit switch  82  into a contacting state, which actuates the limit switch  82 . 
     Turning to  FIG. 3 , specifically, the contact between the seatback frame  12  ( FIG. 2 ) and the box  92  ( FIG. 2 ) may extend the springs  76  enough to separate the button  85  of the limit switch  82  and the bracket  84  causing the limit switch  82  to be in a non-contacting state and actuated. As such, the extension in the springs  76  may detect the box  92  or other obstruction. The actuation of the limit switch  82  may cause a signal to be sent from the limit switch  82  via wiring  88  to the control circuitry  42  ( FIG.1 ), which in turn may cause the control circuitry  42  to send a signal to the solenoid  43  ( FIG. 1 ) to close the valve  44  ( FIG. 1 ). As such, the closed valve  44  does not allow for additional hydraulic fluid to exit the cylinder  68 , and causes the drive mechanism  26  to stop the downward movement of the seatback support  10 . Thus, actuation of the limit switch  82  stops the downward movement of the seatback frame  12 . 
     Indeed, actuation of the limit switch  82  may stop the flow of electric current to the solenoid  43 . For example, there may be an interlock in control circuitry  42  between the limit switch  82  and the solenoid  43  such that they are wired together, with the electric current flowing from the limit switch  82  to the solenoid  43 . Actuation of the limit switch  82  may break the electric current and cut power to the solenoid  43 , which closes the valve  44 . 
     Those of ordinary skill in the art will appreciate that by stopping the downward movement of the seatback frame  12  against the box  92 , further damage to the box  92  may be reduced. Furthermore, when the obstruction is an operator or portion of the operator, stopping the downward movement may limit further pain or discomfort to the operator. 
     The transition of the limit switch  82  from the contacting state to the non-contacting state is illustrated in further detail in  FIGS. 5A-5E .  FIGS. 5A-5E  generally correspond to the scenario illustrated in  FIG. 2 . Beginning with  FIG. 5A ,  FIG. 5A  illustrates the generally upright position of the seatback support  10 , and thus of the seatback frame  12 , illustrated in  FIG. 1 , with the limit switch  82  in a contacting state. In response to a request from the user to recline the seatback frame  12 , the drive mechanism  26  is initiated as disclosed above. For example, the seatback support  10  moves downwardly along track  40  towards the forward end  78  as the cylinder rod  38  moves towards the cylinder  68 , illustrated in  FIG. 5B , in response to the exiting hydraulic fluid. The trunnion  70  also begins to pivot about the axis  71 . 
       FIG. 5C  illustrates the seatback support  10  at the forward end  78 , with the seatback frame  12  in the generally reclined position. Turning to  FIG. 5D , in response to a request by the user to lower the lift arm  6  ( FIG. 1 ), the lift arm  6  lowers with the seatback frame  12  in the reclined position. When the seatback frame  12  contacts an obstruction, such as the box  92  ( FIG. 2 ), the cylinder, which is slideably mounted in the trunnion  70 , begins to exit from the trunnion  70  via the springs  76  ( FIG. 3 ). Specifically, the movement is due to the low force exerted by the springs  76 . Indeed, a gap is illustrated between the protruding portion of the cylinder  68  and the trunnion  70 . The exiting cylinder  68  also moves the bracket  84  away from the button  85 . The exiting cylinder  68  may also cause the seatback support  10  to travel upwards along the track  40  to the rearward end  79 . 
     By  FIG. 5E , the bracket  84  has separated from the button  85  to cause a non-contacting state and actuation of the limit switch  82 . The actuation of the limit switch  82  stops the drive mechanism  26  ( FIG. 1 ) as described hereinabove by causing the valve  44  ( FIG. 1 ) to close. After separation, the springs  76  ( FIG. 3 ) may return the exiting cylinder  68 , and the bracket  84  coupled to the cylinder, towards the trunnion  70 , which may in turn cause the seatback support  10  to move downwardly towards the forward end  78 . As such, the limit switch  82  may return to a contacting state. 
     It is worth noting that the limit switch  82  may be actuated more often when the user utilizes a preprogrammed setting because in such an instance, the user may walk way from the chair  2  as he or she may not need to keep an input member depressed for the movement to occur. 
     In some embodiments, program code may be implemented to prevent (e.g., temporarily prevent) initiation of a downward movement in response to actuation of the limit switch  82 . As such, a user, for example, may not be able to lower the seatback frame  12  any further if he or she accidentally clicks on the input member (not shown) to move the seatback frame  12  downwards instead of the input member to move the seatback frame  12  upwards. Furthermore, in some embodiments, program code may be implemented to automatically initiate another movement. For example, an upward movement of the seatback frame  12  may be initiated via the program code upon actuation of the limit switch  82  to ease a user&#39;s pain or discomfort. 
     In general, the program code may include the routines executed to implement or initiate movements of the chair  2 , whether the program code is implemented as part of an operating system or a specific application, component, program, object, module or sequence of instructions, or even a subset thereof, will be referred to herein as “computer program code,” or simply “program code.” Program code typically comprises one or more instructions that are resident at various times in various memory and storage devices in a computer, and that, when read and executed by one or more processors in the computer such as with control circuitry  42  ( FIG. 1 ), cause performance of the steps necessary to execute steps or elements embodying the various aspects of the movements. 
     Given the typically endless number of manners in which computer programs may be organized into routines, procedures, methods, modules, objects, and the like, as well as the various manners in which program functionality may be allocated among various software layers that are resident within a typical computer (e.g., operating systems, libraries, API&#39;s, applications, applets, etc.), it should be appreciated that the invention is not limited to the specific organization and allocation of program functionality described herein. 
     With reference to  FIG. 1  and  FIG. 6 , the routine  100  in  FIG. 6  illustrates but one example of operating the dental chair  2 , including the operation with respect to the program code. In block  102 , the chair  2  may be provided with the limit switch  82 . For example, the limit switch  82  may be provided during creation of the chair  2  or to retrofit a dental chair. Additionally, the springs  76  ( FIG. 3 ) may also be provided. Next, downward movement of the seatback frame  12  via seatback support  10  of the chair  2  may be initiated in block  104 , with the movement including use of the cylinder  68  and the trunnion  70 . Next, the obstruction may be detected (block  106 ), and in response to the detected obstruction, the limit switch  82  may be actuated to inhibit the downward movement (block  108 ). Furthermore, in response to actuation of the limit switch  82 , the program code may prevent initiation of further downward movement (block  110 ) (e.g., temporarily prevent initiation) and/or may automatically initiate another movement (block  112 ) such as an upward movement of the seatback frame  12  via the seatback support  10 . 
     Next, in some embodiments, the chair  2  may include at least one at electric field sensor (not shown) having capacitive sensing in the seatback frame  12 . The sensor may be operable to detect a change in capacitance created by contact with an obstruction that is a user and actuate the limit switch  82 . The sensor (not shown) may function cooperatively with the limit switch  82 , and may additionally actuate the limit switch  82 . A single sensor may cover, for example, the entire seatback frame  12 . Alternatively, multiple sensors may cover separate portions of the seatback frame  12 . More information about electric field sensors may be found in U.S. patent application Ser. No. 12/262,916, filed on even date herewith by Edelmann and entitled “DEVICE WITH AN ELECTRIC FIELD SENSOR, CONTROL CIRCUITRY, AND A SOLENOID” (MIDTF 472P2), the entire disclosure of which is incorporated by reference herein. 
     While exemplary embodiments have been described in considerable detail herein, it is not the intention of the application 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, with reference to  FIG. 4 , the setup may be reversed, with the limit switch  82  on the protruding portion of the cylinder  68  and the bracket  84  on the top outer surface of the trunnion  70 . 
     Alternatively, as the outer diameter of the trunnion  70  and the outer diameter of the protruding portion of the cylinder  68  may be the same, the limit switch  82  may simply be placed in between the trunnion  70  and the cylinder  68 , on either the trunnion  70  or the cylinder  68 . Moreover, with respect to the trunnion  70 , the limit switch  82  may be generally placed on the vertical outer surface (e.g., directly on the vertical outer surface or indirectly on the vertical outer surface) closest to the protruding portion of the cylinder  68 , instead generally placed on the horizontal outer surface  81  that the limit switch  82  is placed on in  FIG. 4 . Furthermore, the bracket  84  and the button  85  may also be omitted. A limit switch different from that of limit switch  82  may alternatively be utilized. 
     Additionally, with reference to  FIG. 3 , those skilled in the art will appreciate that the arrangement disclosed herein 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 . Other modifications are also possible. 
     Therefore, the invention in its broader aspects is not limited to the specific details or representative devices and method, and illustrative examples shown and described. Accordingly, departures may be made form such details without departure from the spirit or scope of applicant&#39;s general inventive concept.