Abstract:
Numerous structural/patient positioning features are provided for use with a dental x-ray machine. At least the following features are included: an inverted motor arrangement to actuate an outer support column with respect to an inner support column; wiper elements disposed between the inner and outer support columns to provide enhanced electrical grounding therebetween; adjustable roller subassemblies disposed between the inner and outer columns; a flexible electrical cable disposed inside the inner column; a self-aligning base for use with the inner column, the base having symmetric halves; an adaptable handgrip handrail extending from the outer column at compound oblique angles; a drive system for film transport; and a side projection system for patient head positioning, including multiple horizontal light beams.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention is directed to x-ray systems, and more particularly, the present invention is directed to structural and patient positioning features that are used in dental x-ray systems.  
       BACKGROUND OF THE INVENTION  
       [0002]     X-ray systems are commonly used in the dental industry to assist dental professionals. One type of a dental x-ray system uses a diagnostic panoramic technique to take a contiguous radiograph of the entire dentition of the jaw. The panoramic radiograph is achieved by positioning the patient between the x-ray source and a receiving radiosensitive surface. The x-ray source and receiving radiosensitive surface are maintained at a predetermined relationship from each other and revolved around the patient&#39;s head while the x-ray beam is continuously directed at the patient. The dental x-ray system contains many moving and non-moving components and is difficult for one person to assemble due to its considerable weight.  
         [0003]     What is needed are structural and patient positioning features for use with a dental x-ray device that are inexpensive to manufacture, comfortable to use, provide stability to secure the patient&#39;s head position, improve the operation of the dental x-ray device and provide for improved one person assembly of the dental x-ray device.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention relates to a dental x-ray system including a first substantially vertical column and a second substantially vertical column supporting a dental x-ray device, the second column being movable with respect to the first column. At least one wiper is disposed between the first and second columns, the at least one wiper providing electrical signal grounding between the first and second columns produced by the dental x-ray device.  
         [0005]     The present invention further relates to a dental x-ray system including a dental x-ray device for providing a radiograph of a patient&#39;s dentition. A positioning device positions the patient&#39;s head prior to operating the dental x-ray device, and a projection device projects a plurality of substantially horizontal parallel beams onto the patient&#39;s head.  
         [0006]     The present invention yet further relates to a dental x-ray system including a substantially vertical column supporting a dental x-ray device. A positioning device is provided for positioning the patient&#39;s head prior to operating the dental x-ray device. A handrail adjacent the positioning device provides support for the patient during operation of the x-ray device, the handrail comprising a curved portion extending away from the column, the curved portion being substantially coincident with a plane defining a first oblique angle with a first substantially vertical line. The curved portion has an apex, a second line being coincident with the apex, coplanar with the plane and perpendicular to a tangent line coincident with the apex and coplanar with the plane. Except for the apex of the curved portion, each tangent line to the curved surface extends coplanar to the plane defining a second oblique angle with the second line.  
         [0007]     The present invention further relates to a dental x-ray system including a first substantially vertical column and a second substantially vertical column supporting a dental x-ray device, the second column being movable with respect to the first column. At least one pair of opposed roller assemblies is affixed to the second column, each roller assembly interposed between the first and second columns and providing support to the first and second columns along mutually transverse planes.  
         [0008]     The present invention still further relates to a dental x-ray system including a first substantially vertical column and a second substantially vertical column supporting a dental x-ray device, the second column being movable with respect to the first column. A motor is connected to the second column, the motor having a threaded shaft extending toward the first column. A threaded sleeve is in threaded engagement with the shaft, the threaded sleeve extending away from the second column. The motor controllably moves the second column with respect to the first column by rotating the shaft with respect to the sleeve.  
         [0009]     The present invention still yet further relates to a dental x-ray system including a column supporting a dental x-ray device, the column having a base and a first bracket. A floor mounted second bracket has at least one protrusion formed therein, the base having at least one aperture for receiving the at least one protrusion. A wall mounted third bracket is located substantially vertically above the floor mounting bracket for substantially simultaneously receiving the first bracket while the base is receiving the second bracket.  
         [0010]     An advantage of the present invention is that it can be inexpensively manufactured.  
         [0011]     A further advantage of the present invention is that it improves patient comfort.  
         [0012]     A yet additional advantage is that it secures the patient&#39;s head position.  
         [0013]     A still further advantage of the present invention is that it improves the operational reliability of the dental x-ray device.  
         [0014]     An additional advantage of the present invention is it provides for improved one person assembly of the dental x-ray device.  
         [0015]     A still yet further advantage is that it has a concealed flexible electrical cable carrier to accommodate vertical height adjustment of the dental x-ray device of the present invention.  
         [0016]     A further advantage is an inverted motor and push rod for raising the outer column, the motor being mounted to the top of the outer column for improved access to the motor of the dental x-ray device of the present invention.  
         [0017]     A yet additional advantage is an electrical ground wiper for improved electromotive compatibility of the dental x-ray device of the present invention.  
         [0018]     A still further advantage is a separate roller subassembly that is easily installed to the columns of the dental x-ray device of the present invention.  
         [0019]     An additional advantage is a self-aligning base to aid in the installation of the dental x-ray device of the present invention.  
         [0020]     A still yet further advantage is a tapered self-aligning wall mounted bracket to aid in the installation of the dental x-ray device of the present invention.  
         [0021]     A further advantage is a symmetric base that is stackable to minimize storage space and shipping costs of the dental x-ray device of the present invention.  
         [0022]     A yet additional advantage is a removable caster assembly to ease one-man installation of the dental x-ray device of the present invention.  
         [0023]     A still further advantage is a motor for use with the image capture subassembly that is driven along a separate roller subassembly having components directly coupled to the motor to reduce the number of moving parts of the dental x-ray device of the present invention.  
         [0024]     An additional advantage is adaptable handgrip railing to aid with patient positioning associated with use of the dental x-ray device of the present invention.  
         [0025]     A still yet further advantage is the provision of multiple horizontal lines to be adaptable to determine the Frankfort plane for differently sized patients of the dental x-ray device of the present invention.  
         [0026]     Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]      FIG. 1  is a perspective view of a dental apparatus of the present invention.  
         [0028]      FIG. 2  is an exploded view of an embodiment of a base for a dental apparatus of the present invention.  
         [0029]      FIG. 3  is a partial perspective view of a motor providing vertical adjustment for a dental apparatus of the present invention.  
         [0030]      FIG. 4  is a cross section of an embodiment including grounding wipers and a roller assembly taken along line  4 - 4  of  FIG. 1  for a dental apparatus of the present invention.  
         [0031]      FIG. 5  is a perspective view of a roller assembly of the present invention.  
         [0032]      FIG. 6  is a perspective view of an adjustable electrical wiring cable of the present invention.  
         [0033]      FIG. 7  is a cross section of an embodiment including a wall bracket having angled arms for supporting the inner column taken along line  7 - 7  of  FIG. 1  for a dental apparatus of the present invention.  
         [0034]      FIGS. 8-9  are cross sections of an embodiment of a caster assembly taken along line  7 - 7  of  FIG. 1  for a dental apparatus of the present invention.  
         [0035]      FIG. 10  is an exploded view of a motor and components associated with exposing a radiosensitive surface for a dental apparatus of the present invention.  
         [0036]      FIG. 11  is an elevation view of projected reference lines onto the side of a patient&#39;s face for locating a patient&#39;s Frankfort plane for use with a dental apparatus of the present invention.  
         [0037]      FIGS. 12-14  are differently oriented views of a handrail of a dental apparatus of the present invention.  
         [0038]      FIG. 15  is a view taken along line  15 - 15  of  FIG. 12  of a handrail of a dental apparatus of the present invention.  
         [0039]      FIG. 16  is a reverse assembled perspective view of  FIG. 2  of a dental apparatus of the present invention.  
         [0040]      FIG. 17  is a reverse exploded partial view of  FIG. 1  of a dental apparatus of the present invention.  
         [0041]      FIG. 18  is an exploded view of components associated with exposing radiographic film to electron beams for a dental apparatus of the present invention.  
         [0042]      FIG. 19  is an assembled perspective view of the components associated with exposing radiographic film to electron beams from  FIG. 18  for a dental apparatus of the present invention. 
     
    
       [0043]     Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0044]     One embodiment of a dental apparatus  10  of the present invention is depicted in  FIG. 1 . Preferably, the dental apparatus  10  includes a base  16  in which is set an inner column  12 , the inner column  12  extending upwardly from the base  16 . An outer column  14  slides along the length of inner column  12  to controllably vary the height of outer column  14  as measured from the floor. A wall-mounted bracket  13  secures inner column  12  in a substantially vertical position. Outer column  14  slidingly supports a handrail  20  and a chinrest  18 . Handrail  20  can include one or more bars extending away from outer column  14  in a direction that is ergonomically friendly for a patient (not shown) to grasp while the dental apparatus  10  is in operation. The handrail  20  permits the patient to conveniently stabilize her position once the patient&#39;s chin has been placed and positioned on the chinrest  18 . Adjacent the end of the outer column  14 , a cantilevered member  22  facing away from the floor rotatably carries an inverted U-shaped structure  24  about a substantially vertical axis  25 . The U-shaped structure  24  includes a first projection  26  containing an x-ray source and a second projection  28  containing a radiosensitive material or a plurality of radiosensitive receptors or sensors, the projections  26 ,  28  being connected to and supported by a web  27 . During operation of the dental apparatus  10 , the projections  26 ,  28  are rotated about the head of the patient, producing a contiguous radiograph of the entire dentition of the patient&#39;s jaw.  
         [0045]     Referring to  FIGS. 1-2  and  16 - 17 , a base  16  preferably receives inner column  12  to ease positioning of the dental apparatus  10 . Base  16  includes a base plate  200  that is supported by and fastened to a backing plate  202 . Base plate  200  and backing plate  202  are secured to the bottom of the inner column  12 . Preferably, a pair of angles  204  are affixed to the base plate  200  adjacent to a proximal end  206  of the base plate  200 , the angles  204  spaced to contact the lower end of the inner column  12  on three sides. To further stabilize the inner column  12 , preferably a pair of flanged supports  212  are inserted adjacent to a distal end  210  of the base plate  200  and the inner column  12 . One flanged end of each flanged support  212  is secured to the distal end  210  and the other flanged end is secured to the inner column  12 . The base plate  200  and backing plate  202  are secured to the floor or wall of a desired location by a floor mounting plate  214 . The floor mounting plate  214  preferably is an angle having a pair of perpendicular legs  219 . On the leg  219  of the floor mounting plate  214  in contact with the floor, at least one, and preferably two, pins  216  extend upwardly therefrom. At least one aperture  218  is formed in either or both of the legs  219  of the floor mounting plate  214  to receive a fastener to secure the floor mounting plate  214  in position. Once the floor mounting plate  214  is installed, the base  16  can then be secured in position by directing apertures  220  of the backing plate  202  into engagement with the pins  216 . To further ease this engagement, either or both of the pins  216  and the apertures  220  can be tapered.  
         [0046]     In a preferred embodiment, as shown in  FIG. 17 , the base plate  200  and backing plate  202  are hidden from view from exterior of the inner column  12  by a proximal cap  222  and a distal cap  224 . Additionally, the distal cap  224  is sized to further hide electrical components  226  from view from exterior of the distal cap  224 , the proximal and distal caps  222 ,  224  providing a pleasing appearance to the dental apparatus  10 .  
         [0047]     In a preferred embodiment, such as  FIG. 2 , the base  16  is symmetric about a vertical plane that is coincident with the midspan of the proximal end  206 . Stated another way, the halves of the base  16  define mirror images of each other. Such symmetry is advantageous as it is amenable to compactly arranging multiple bases  16  together, such as by stacking. Benefits from the compact multiple base  16  stacking configurations include reduced shipping and packaging costs as well as a reduced storage space requirement for the bases  16 .  
         [0048]     Referring to  FIG. 3 , the orientation of a column motor  58  is now discussed. Motor  58  controls the movement of outer column  14  with respect to inner column  12 . Preferably, motor  58  achieves controllable movement of outer column  14  by selectively extending or retracting a threaded shaft  62  with respect to a threaded sleeve  60 , which shaft  62  is connected to the motor  58  and is of fixed length. In a preferred embodiment, sleeve  60 , which is in threaded engagement with the shaft  62  at one end, extends inside a boss  66  at the other end that is affixed to the base  16  of the inner column  12 . Preferably, a pin  65  extends through the boss  66  and into the sleeve  60  to prevent the sleeve  60  from rotating about the axis along its length. Sleeve  60  and shaft  62  support the weight of the outer column  14  and components extending from the outer column  14 . Actuating the motor  58  to drive the shaft  62  into rotational movement in one direction decreases the amount of threaded engagement between sleeve  60  and the shaft  62 , raising the outer column  14  with respect to the inner column  12 . Similarly, actuating the motor  58  to drive the shaft  62  into rotational movement in the other direction increases the amount of threaded engagement between sleeve  60  and the shaft  62 , lowering the outer column  14  with respect to the inner column  12 .  
         [0049]     As the length of shaft  62  is increased by actuation of the motor  58 , i.e., the length that shaft  62  extends past the end of sleeve  60 , the outer column  14  is similarly raised by an amount equal to the increase in the length of the shaft  62 . It is to be understood that motor  58  may be powered by at least one of electrical, hydraulic or pneumatic power from a suitable source (not shown). It is notable that in a preferred embodiment, the motor  58  is secured adjacent to the top of the outer column  14  in an inverted position, providing ease of access for installing or servicing of the motor  58 , while minimizing the number of components.  
         [0050]     Referring to  FIGS. 4-5 , grounding wipers  68  preferably each include a base  70  from which an upper wiper element  72  and a lower wiper element  74  outwardly extend. Base  70  is preferably affixed to an inside surface  71  of the outer column  14 , the upper and lower wiper elements  72 ,  74  each extending sufficiently outward to contact a corresponding outside surface  73  of the inner column  12 . The spring-like wiper elements  72 ,  74 , which are composed of electrically conductive material, such as a metal, constantly contact or wipe against the inner column  12  at all times, i.e., both while the outer column  14  is stationary with respect to the inner column  12  and while the outer column  14  is moving with respect to the inner column  12 . By virtue of the increased surface area contact between corresponding adjacent surfaces  71 ,  73  of the outer and inner columns  14 ,  12 , the wiper elements  72 ,  74  provide substantially enhanced electrical grounding contact or electromagnetic compatibility (EMC) filtering between these surfaces. Importantly, this enhanced electrical grounding contact achieves high frequency signal grounding to reduce radiated electromagnetic interference produced by the x-ray system components, providing improved performance by the dental apparatus  10 .  
         [0051]     Referring to  FIGS. 4, 5 ,  8  and  9 , to provide a reduced friction interface between the inner and outer columns  12 ,  14  and additionally protect the wipers  68  from being crushed or damaged by the corresponding surfaces  71 ,  73  of the outer and inner columns  14 ,  12 , a pair of opposed roller assemblies  230  can be used. One roller assembly  230  is preferably secured to each opposed outboard side  236  of the outer column  14 . As shown in  FIG. 5 , a front wall  238  of the outer column  14  is removed for clarity. Preferably, a plate  232  is secured to the outboard side  236  by a plurality, such as two, fasteners  234 . The heads of the fasteners  234 , as well as the other fasteners associated with adjustment of the casters to be discussed in further detail below, are accessible through apertures  240  formed in the outer column  14  from exterior of the outer column  14  for ease of adjustment. Actuating the fasteners  234  in one direction urges the plate  232  away from the outboard side  236 . Similarly, actuating the fasteners  234  in the other direction urges the plate  232  toward the outboard side  236 .  
         [0052]     Preferably, there are sets of transversely oriented sets of casters associated with roller assembly  230 . The first set of casters is a roller subassembly  242  that includes a frame  244  which is interposed between plate  232  and outboard wall  236  and secured to the plate  232 . A portion of the frame  244  extends through a slot  262  formed in the plate  232  and rotatably carries a caster  246  that rotates about an axis  248  which is substantially perpendicular to the rear wall  238  of the outer column  14 . A pair of fasteners  264  adjustably secures the frame  244  to the plate  232 . That is, activating the head of the fastener  264  in one direction urges the frame  244  toward the plate  232 , and similarly, activating the head of the fastener  264  in the other direction urges the frame  244  away from the plate  232 . The heads of fasteners  264  are accessible through apertures  240  formed in the outer column  14 . Additionally, actuating the frame  244  toward the plate  232  urges the caster  246  toward one of opposed channels  256  formed in the inner column  12 . The channel  256  includes a pair of opposed surfaces  258  separated by a recessed surface  260 . Thus, the periphery of caster  246  contacts the recessed surface  260  ( FIG. 8 ). It is appreciated by those skilled in the art that opposed sets of casters  246  of opposed roller subassemblies  242  maintain alignment between the inner and outer columns  12 ,  14  in a plane parallel to the rear wall  238  of the outer column  12 .  
         [0053]     The other set of casters includes a fastener  252  that rotatably carries a caster  250  about an axis  254 , which axis  254  is substantially parallel to rear wall  238  and substantially perpendicular to outboard wall  236 . The heads of fasteners  252  are accessible through apertures  240  formed in the outer column  14 . Activating the head of the fastener  252  in one direction urges the caster  250  between opposed surfaces  258  of the channel  256  of the inner column  12 , and similarly, activating the head of the fastener  252  in the other direction urges the caster  250  away from the opposed surfaces  258  of the channel  256  of the inner column  12 . Thus, when the caster  250  is properly installed, the periphery of caster  250  contacts the opposed surfaces  258  of column  12  ( FIG. 9 ). It is appreciated by those skilled in the art that opposed sets of casters  250  maintain alignment between the inner and outer columns  12 ,  14  in a plane parallel to the outboard walls  236  of the inner column  12 . Therefore, caster  250  and caster  246  of roller subassembly  242  provide enhanced stability in mutually transverse planes between the inner and outer columns  12 ,  14 .  
         [0054]     Referring to  FIG. 6 , a flexible electrical cable  94  is inserted inside the inner column  12 . The cable  94  is of sufficient length to provide electrical power to the dental apparatus  10  when the outer column  14  is extended to its uppermost position. However, to accommodate for vertical adjustment of the outer column  14  to other positions, the cable  94  preferably defines a lower portion  93  that extends from adjacent the plate  30  adjacent the floor of the room enclosing the dental apparatus  10  to an upper loop  95 . Since the upper loop  95  can accommodate the lowest vertical position of the column  14 , lower portion  93  does not need to move, therefore the position of the upper loop  95  can be fixed to the inside of the inner column  12  if desired. Similarly, an upper portion  97  of the cable  94  extends between the upper loop  95  and the top of the outer column  14 . One end of the upper portion  97  corresponds to the top of the outer column  14  and is fixed, while the other end of upper portion  97  corresponds to the upper loop  95 . Thus, while the actual length of the upper portion  97  can vary, it consists of a single substantially vertical run of the cable  94 . In other words, the upper portion  97  includes a length of the cable that hangs substantially vertical due to gravity.  
         [0055]     Providing the adjustment to the length of the upper portion  97  is a transition region  99  between the upper loop  95  and a lower loop  96 . One portion of the transition region  99  is defined by a portion of the cable  94  that extends from lower loop  96  toward the upper loop  95 . The other portion of the transition region  99  is defined by a portion of the cable  94  that extends from the lower loop  96  toward the upper portion  97  that is between the lower loop  96  and the upper loop  95 . Stated another way, the transition region  99  includes two substantially vertically oriented portions of the cable  94  of equal length (transition length). For example, a change in vertical height from the floor from an initial height  98 , referred to as h i , to an added height  102 , referred to as h a , must be accounted for by a corresponding change in the transition length, i.e., from an initial transition length, l t1  (measured from upper loop  95  to lower loop  96 ) to a final transition length l t2  (measured from upper loop  95  to raised lower loop  100 ). It can be shown that any increase or decrease in the length of the upper portion  97  (h a ) corresponds to a change of the length of the transition region  99  equal to one half of the length change of the upper portion  97 . It is to be understood that the position of the upper loop  95  can be adjusted to any position between the floor and the highest position adjacent the top of the outer column  14 , which also means that the position of the upper loop  95  can move during vertical adjustment of the outer column  14 , and that the transition region  100  can include more than two portions of the cable  94 , so long as the cable  94  can provide electrical power to the dental apparatus  10  irrespective of the position of the outer column  14  with respect to the inner column  12 . A carrier or guard may be used to ensure the correct cable drape.  
         [0056]     By positioning the cable  94  inside the inner column  12 , not only is the cable  94  protected from damage by objects exterior of the inner column  12 , but substantially all of the cable  94  is hidden from view, which otherwise detracts from the appearance of the dental apparatus  10 .  
         [0057]     Referring to  FIGS. 1, 2  and  7 , wall-mounted bracket  13  includes a pair of opposed arms  104  secured at a predetermined spacing by a web  106  to secure the dental apparatus  10  in position to a wall  108 . Preferably, each arm  104  is substantially perpendicular to the wall  108 . In a preferred embodiment, a bracket  110  is affixed to the inner column  12 , slots  118  being formed in the outer column  14  to permit movement of the outer column  14  with respect to the inner column  12  and the bracket  110 . Bracket  110  includes a web  112  having opposed arms  114  that extend outwardly therefrom, each arm  114  terminating at an inwardly directed angled portion  116 . Bracket  13  is positioned at a predetermined height above the base  16  so that the midspan of the web  106  of the bracket  13  is plumb, or vertically positioned with respect to the midspan of the base  16 .  
         [0058]     After the bracket  13  has been affixed to the wall  108  plumb to the base  16 , the dental apparatus  10  can be easily aligned and installed. The base plate  200  and backing plate  202  secured to the lower end of the inner column  12  are directed into engagement with the floor mounting plate  214 , as previously discussed. Simultaneously, the inner column  12  is brought toward the wall  108  into engagement with the bracket  13 . The ends of the angled portions  116  of the bracket  110 , which are closer together than the distance between the arms  104  of the bracket  13 , are directed between the arms  104 . The angled portions  116  of bracket  110  received between the arms  104  of bracket  13  are further directed between the arms  104  so that a portion of the arms  114  is also inserted between the arms  104 . The arms  114  of bracket  110  are sized to sufficiently engage the arms  104  of bracket  13  so that once the base plate  200  and backing plate  202  are directed into engagement with the floor mounting plate  214 , the arms  114 ,  104  of respective brackets  110 ,  13  can be secured together by fasteners (not shown). In other words, the angled portions  116  of the bracket  110  provide a self-alignment feature to greatly simplify assembly of the dental assembly  10 .  
         [0059]     Referring back to  FIGS. 1-2 , the assembly of the dental apparatus  10 , while straightforward, as previously discussed, can be somewhat cumbersome for one-person assembly, due to both the size and weight of the components. To greatly simplify the installation of the inner column  12  into the base  16 , as shown in  FIG. 2 , i.e., eliminate the need to lift and then guide the end of the inner column  12 , a removable caster  40  is provided. Preferably, the caster assembly  40  includes a frame  42  configured to rotatably carry a caster  44  adjacent each end of the frame  42 . The caster assembly  40  is secured to the lower portion of the inner column  12 , such as by fasteners  46 . One skilled in the art can appreciate that the caster assembly  40 , which preferably includes a pair of casters  44  which are spaced apart from each other, provides a stable rolling platform by which to move the dental apparatus  10 , such as directing the dental apparatus  10  into engagement with the floor mounting plate  214  and bracket  110  as previously discussed. Preferably, after the dental apparatus  10  is secured, the caster assembly  40  can be disassembled simply by loosening and removing the fasteners  46  from the inner column  12 . Further, in a preferred embodiment as shown in  FIG. 17 , the disassembled caster assembly  40  can be stored beneath a cover  48  of the cantilevered member  22  for possible future use, such as if the dental apparatus  10  is moved to a different location.  
         [0060]     Referring to  FIGS. 1, 10 ,  18  and  19 , projection  28  includes components relating to moving the radiographic film during exposure to the electron beam emitted by x-ray components contained in projection  26 . Disposed in projection  28  is a housing  270  having an aligned slot  121  formed in the projection  28  and the housing  270  through which electron beams can pass to expose the radiographic film (not shown). Additionally, housing  270  includes aligned openings  272 ,  274  through which a tray  276  can extend, and a guide  282  to maintain the tray  276  in moving alignment with the openings  272 ,  274 . A threaded rod  278  is secured to the housing  270 , a motor  284  being placed in meshing engagement with the threaded rod  278 . A housing  280  secures the motor  284  and the tray  276  together so that the housing  280 , motor  284  and tray  276  move in unison upon actuation of the motor  284 . Actuation of the motor  284  in one direction urges the housing  280 , motor  284  and tray  276  to move in unison along the threaded rod  278  toward the opening  274  of housing  270 . Similarly, actuation of the motor  284  in the other direction urges the housing  280 , motor  284  and tray  276  to move in unison along the threaded rod  278  toward the opening  272  of housing  270 . In operation, this movement exposes radiographic film placed in the tray  276  to electron beams passing through slot  121  formed in the housing  270 . Preferably, electrical wiring  286  provides electrical power to the motor  284 . By virtue of the housing  280 , motor  284  and tray  276  moving in unison with respect to the housing  270 , the number of components required by the dental apparatus  10  is reduced, as is the space required in projection  28 , thereby reducing both the size and expense associated with manufacturing the projection  28  and its associated components.  
         [0061]     Referring to FIGS.  1 ,  12 - 14 , handrail  20  provides a symmetric, multiple position handhold for a patient for steadying herself while using the chinrest  18  of the dental apparatus  10 . Handrail  20  which is positioned beneath the chinrest  18  includes a curved portion  162  that is substantially coplanar to define a plane which is disposed at an oblique angle  170 , preferably an acute angle with respect to the vertical surface of the inner column  12 . The midspan of the curved portion  162  includes an apex  174 . As shown in  FIG. 15 , a line  176  is coincident with apex  174  and with the plane defined by the curved portion  162 . Line  176  is perpendicular to a line  180  that is tangent to the curved portion  162  and coincident with both apex  174  and with the plane defined by the curved portion  162 . As a result, other than apex  174 , any line tangent to a point on the curved portion  162  that is coplanar with the plane that is coincident with the curved portion  162 , such as  178 , defines an oblique angle with line  176 , the angle preferably being an acute angle. Stated another way, the angle between lines  178  and  176  decrease in magnitude gradually as the curved portion  162  proceeds toward the elbow portion  164 . Therefore, the curved portion  162  provides a continually changing combination of compound oblique angles with respect to the above-identified reference surfaces. By virtue of this continually changing combination of compound oblique angles, a patient can find an especially comfortable position at which to grasp the handrail  20 . It is to be understood that since each side of the handrail  20  contains this continually changing combination of compound oblique angles, the patient can grasp the handrail  20  at different positions, each corresponding to a different combination of compound oblique angles, or alternately, can grasp different positions on the same half of the handrail  20  if desired. It is to be understood that the purpose of the handrail  20  is to provide a grasping arrangement for each patient that is ergonomically friendly for that patient, allowing the patient to position herself in a consistent, stable manner in order to achieve the highest quality radiographs.  
         [0062]     Referring to  FIG. 11 , a projection technique of the present invention is shown for enhancing patient positioning while the patient&#39;s chin is positioned on the chinrest  18 , irrespective the size of the patient&#39;s head. Typically, a single horizontal light beam is emitted by a light source of a dental apparatus to help provide a reference point for orienting a patient&#39;s head prior to processing a radiograph. The patient&#39;s reference, referred to as a Frankfort plane, is a line connecting the superior border of the external auditory meatus with the infraorbital rim, as is well known in the art. In a preferred embodiment, as shown in  FIG. 11 , multiple horizontal light beams  124 ,  126 ,  128 ,  130 , as well as a single vertical beam  122  to align with the patient&#39;s cuspid, terminating all horizontal beams on the right extent, are emitted by a light source (not shown) of the dental apparatus  10  to help provide a reference point for a patient&#39;s head  132  resting on chinrest  18 . By virtue of providing the multiple light beams, such as the four shown, or more, if desired, one of the light beams will sufficiently correspond to the Frankfort plane, such as light beam  126  for the patient&#39;s head  132  as shown in  FIG. 11 . Thus, additional adjustment of the projected light beam is not required, saving both time and effort. Further, the light beam projections can originate from an existing cuspid location light (not shown) on the dental apparatus  10 , further reducing cost, power usage and the number of components.  
         [0063]     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.