Abstract:
An illumination assembly for a medical diagnostic instrument, includes an open ended lamp housing, an incandescent lamp disposed within the housing. A peripheral sealing member is disposed in intimate contact with the exterior surface of the lamp envelope such that initial energization of said lamp causes the sealing member to create a substantial fluid-tight seal with the lamp to protect the interior of the housing, including the electrical contacts of the assembly.

Description:
FIELD OF THE INVENTION 
     This invention relates to the field of illumination devices and in particular to the development of a fluid-tight seal in a lamp housing. 
     BACKGROUND OF THE INVENTION 
     There are known illumination assemblies in the medical diagnostic field, such as the 78010 illuminator assembly manufactured by Welch Allyn Inc., in which a miniature halogen or other miniature incandescent lamp is retained within the confines of a lamp housing. The lamp housing is threaded or otherwise disposed into the distal end of a assembly receptacle or assemblage containing a number of electrical contacts and having a proximal end with a strain relief and a cord containing electrical connectors extending to a power supply, such as a transformer. The assembly receptacle, including the lamp housing, can be implanted into the confines of a handle of a disposable vaginal speculum, such as those described in U.S. Pat. No. 3,176,047, the speculum being equipped with a light conducting end that is configured in order to direct light from the miniature contained halogen bulb to permit conduction of pelvic examinations. 
     During use in the vaginal speculum, the above described illumination assembly is subsequently exposed to fluids, requiring that the lamp be cleaned and sterilized following use or that the life of the lamp is shortened prematurely due to the presence of fluids entering the housing and corrupting the electrical leads and lamp contacts. To date, there has not been provided an effective technique for providing a fluid-tight seal for a lamp in an illumination assembly such as those described above. 
     Referring to  FIG. 1 , and in the assembly of a typical lamp housing, cement, epoxy or other suitable applied adhesive  202  is added into secure the position of the miniature incandescent lamp  200  within the lamp housing  204  as the electrical leads  212  of the lamp are drawn through the bottom of the lamp housing for attachment to the remainder of the illuminator assemblage and more particularly to a contact  216 . It is essential during this process that the distal end  220  of the lamp  200  be maintained properly at the distal end  224  of the lamp housing  200 . Without the adhesive  202 , the lamp  200  would not hold its desired position within the housing when the leads  212  are drawn to the contact  216 . 
     The preceding manufacturing process fails to provide a fluid-tight seal for the lamp housing in that moisture migrates through microfissures that are formed in the adhesive and as readily apparent fails to provide any form of protection for the lamp itself as fluids can easily permeate the boundary between the envelope of the bulb and the interior of the housing. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to overcome the above-noted deficiencies of the prior art. 
     It is therefore another primary object of the present invention to provide an illumination assembly for a medical diagnostic or other instrument that is exposed to fluidic environment(s) capable of shortening the effective life of such instruments. 
     Therefore and according to a preferred aspect of the invention, there is provided an illumination assembly comprising a miniature incandescent lamp fitted within a housing, and an elastomeric sealing member disposed between an inner surface of the housing and the outer surface of the incandescent lamp, wherein the sealing member is placed in intimate contact with the lamp such that the sealing member fuses to said lamp while maintain a permanent substantially fluid-tight seal. 
     Preferably, the sealing member is made from a similar material as the glass envelope of the lamp such that the fusion process produces a coalescence between the envelope of the lamp and the exterior surface of the sealing member, thereby resulting in a highly effective seal without destroying the integrity of the sealing member or interfering with the illumination capacity of the miniature incandescent lamp. 
     Preferably, the sealing member is a silicon O-ring that is fitted within an peripheral inner slot provided within the lamp housing, the seal being initiated the first time the lamp is energized. Preferably, the ring is placed into compressive contact with the lamp prior to energization, the slot providing an interference fit with the housed bulb. 
     According to another preferred aspect of the present invention, there is provide a method of effectively sealing a lamp within a lamp housing, the method including the steps of: 
     disposing a miniature incandescent lamp within a lamp housing; 
     placing the exterior surface of a sealing member disposed in said lamp housing into intimate contact with the envelope of a miniature incandescent lamp; wherein 
     energizing said lamp creates a substantially fluid tight seal between said lamp and the sealing member. 
     An advantage of the present invention is that the formation of a fluid tight seal within the lamp housing protects the interior of the housing from damage that may occur environmentally during use of the illuminator in a medical diagnostic instrument. As a result, the life of the instrument, including that of the lamp, is effectively increased. 
     Yet another advantage is that the created seal allows the illuminator assembly to be soaked for cleaning and sterilization purposes, a feature heretofore not possible with these assemblies. 
     These and other objects, features and advantages will become readily apparent from the following Detailed Description which should be read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial side sectional view of a lamp housing for an illuminator assembly made in accordance with the prior art; 
         FIG. 2  is a top perspective view of a vaginal speculum using the illuminator assembly of the present invention; 
         FIG. 3  is a side view of a portion of the illuminator assembly including a lamp housing made in accordance with the present invention; 
         FIG. 4  is partial side sectioned view of the lamp housing of  FIG. 3 ; 
         FIG. 5  is an exploded view of the illuminator assembly of  FIG. 3 , including an in-line illuminator switch assembly; and 
         FIG. 6  is an enlarged view of the sealing portion of  FIG. 4  taken between the lamp and the sealing member. 
     
    
    
     DETAILED DESCRIPTION 
     The following description relates to a specific illumination assembly for use in a vaginal speculum. It will be readily apparent to one of sufficient skill in the field, however, that the present invention can be utilized in literally any medical or other instrument that includes an illumination assembly and is exposed to a fluidic environment. 
     Referring to  FIG. 2 , and as a point of background, an illuminator assembly  40  in accordance with the present invention is shown as used with a disposable vaginal speculum  300 . In brief, the disposable vaginal speculum  300  includes three main interconnected components; namely, a fixed blade member  304 , a movable blade member  308  and a slide member  312 . Each of the above components are made from a clear, tough plastic material, such as acrylic or polystyrene, in which the fixed blade member  304  includes a trough shaped blade and a hollow leg  316 . The slide member  312  includes a forked upper end  320  that receives the movable blade member  308  which is pivotally attached thereto, including a lever portion  324 , the slide member further including a lower tongue  332  having ratchet teeth that engage with corresponding teeth provided on the rear side of the hollow leg  316  of the fixed blade member  304  of the speculum  300  to provide adjustment therebetween. Additional details concerning the herein described disposable vaginal speculum can be found in U.S. Pat. No. 3,716,047, the entire contents of which are herein incorporated by reference. 
     The hollow leg  316  of the fixed blade member  304  of the disposable vaginal speculum  300  includes a slot  336  that is sized for receiving an illuminator assembly as well as an interior curved light bar (not shown) that receives the light from a miniature incandescent lamp contained in the illuminator assembly and directs it along a longitudinal axis of the fixed blade member  304 . Details concerning the curved light bar can also be found in the previously incorporated U.S. Pat. No. 3,716,047. 
     Referring to  FIGS. 2 and 3  and  5 , the illuminator assembly  40  includes an illuminator assemblage  44  in the form of a plastic outer section  41  having a molded cavity sized for fitting an elongate metal tube  43  therein. The distal end of the assemblage  44  includes a contact pin  45  that is fitted into a contact socket  47  surrounded by an insulator  51 , each of which are fitted into the distal end of the contained metal tube  43 . A lead wire  53  attached to the contact socket  47  extends through the interior of the metal tube  43  and a wing band  55  and a wire splice  61  are provided at the proximal end thereof, retaining the end of the extending lead wire and guiding same to the interior of a grippable strain relief  48  to interconnect same with a set of electrical conductors. The grippable strain relief  48  includes a distal end having a cavity sized for engaging the proximal end of the plastic section  41 , thereby forming the assemblage  44 . 
     An insulated electrical cable  52  is tethered to the assemblage at the grippable strain relief  48  at one end, the cable containing the appropriate electrical conductors  62  and to an in-line illumination switch assembly  56  at its opposing end. The in-line illumination switch assembly  56  includes an elongated housing  63  having a cover  65 . The housing defines an enclosure having a rocker switch  67  interposed in the center thereof. The cover  65  includes an opening retaining a flexible boot  69 , the boot being made from santoprene or an equivalent material, covering the switch  67 , the cover being attached to the top of the housing by a set of fasteners  71 . Another electrical cable  73  extends from the opposite side of the in-line illuminator switch assembly  56 , this cable including a proximal end terminating in a plug  58  having a strain relief  75  and a pre-molded body including a set of male connector pins  80  for engaging a corresponding plug  59  extending to a power supply, such as a transformer  50  along a corresponding electrical cable  54 . A wing band  83  collects the ends of the electrical conductors  62  within the cable for electrical interconnection to the connector pins  80 . Preferably, the in-line illumination switch assembly  56  includes strain reliefs on either side for the attached electrical cables  52 ,  73 . 
     Still referring to  FIGS. 2 and 3 , a lamp housing  64 , not shown in  FIG. 5 , is retained by the illuminator assemblage  44  that is releasably mounted by screw threads to permit replacement thereof at the distal end of the assemblage. 
     Referring to  FIG. 4 , the lamp housing  64  of the present invention is detailed. The miniature incandescent lamp  60 , such as a Model 07800 6-volt halogen lamp manufactured by Welch Allyn, Inc., is disposed within a cylindrical open-ended housing  64 , made from nickel-plated brass, the distal end  66  of the lamp being arranged to be coplanar with the distal end  70  of the housing. It should be point out that the lamp housing can alternatively be made from other suitable electrically conductive materials, such as, for example, stainless steel. A set of lamp leads  74  extend from the lamp filament  78  through the bottom of the glass bulb envelope  82 . The lamp leads  74  extend through the entire length of the lamp housing  64  and terminate at an electrical contact  86 , this contact being added to the proximal end  90  of the lamp housing by an insulator  94 . 
     An elastomeric sealing member, in this instance, an O-ring  98 , is disposed in a circumferential slot  102  that is formed in the interior of the open ended lamp housing  64 . The O-ring  98  according to this embodiment is made from untreated silicone wherein it is desirable to provide a sealing member made from a material as similar as possible to that of the glass bulb envelope  82 . As noted, the O-ring  98  is elastomeric. According to the present embodiment, the O-ring is approximately on or about  70  Durometer, Shore A. The O-ring  98  engages the exterior of the glass bulb envelope  82  and forms an interference fit therewith, the O-ring being disposed substantially close to the distal end  70  of the housing  64 . A sleeve  106  made from a heat-resistive material, such as ultem or other suitable material, covers the exterior of the lamp housing  64  to prevent injury or burns when it is touched during or immediately after lamp energization. 
     The O-ring  98  extends only partially into the circumferential slot  102  and is therefore placed into compressive contact with the exterior of the glass bulb envelope  82 . Referring to  FIG. 6  and upon energization of the lamp  60 , the exterior surface of the O-ring  98  exceeds its transition temperature due to the heat generated by the lamp causing the incident exterior contacting surface of the O-ring  98  to coalesce with that of the glass bulb envelope  82 , creating a bond  108  and therefore a highly effective peripheral fluid-tight static seal which remains even after the lamp has been deenergized. 
     In the manufacturing process and referring most particularly to  FIG. 4 , the lamp  60  is initially placed into the open-ended lamp housing  64 , similarly to that of  FIG. 1 . Cement or other epoxy (not shown) can be used, if desired, to properly maintain the lamp&#39;s datum to the upper surface of the illumination assembly  40 , though the compressive contact of the O-ring  98  will accomplish same to permit the lamp leads  74  to be properly routed and attached to the contact  86  without displacing the lamp out of position. Following the interconnection of the lamp  60  to the contact  86  of the illuminator assembly  40 ,  FIG. 2 , the lamp can be initially energized to create the fluid-tight seal prior to use or the seal can be created during first use of the assembly. The seal created is permanent due to the coalescence and primarily due to ionic chemical bonds that are produced between the sealing member  98  and the lamp bulb envelope. 
     Once assembled, the miniature incandescent lamp  60  can be energized selectively by means of the in-line switch assembly  56 . Electrical contact is established between the contact  86  of the lamp  60  and the contact pin  45  extending through lead wire  53  to the electrical conductors  62  in the electrical cable  52  extending to cable  73  and ultimately to the transformer  50 . The in-line illumination switch assembly, through boot  69  enabling rocker switch  57 , energizes the lamp by completing or closing the above connection selectively, wherein the boot provides a seal to the interior of the assembly housing  63 . 
     In use, the illuminator assemblage  44  is placed within the slot  336  of the fixed blade member  204  of the disposable vaginal speculum  200 , in the manner depicted according to  FIG. 2  for the examination of a patient. Due to the fluid-tight seal formed between the lamp  60  and the lamp housing  64 , the effective life of the lamp and the illuminator assembly  40  is effectively increased. 
     PARTS LIST FOR FIGS.  1 – 6   
     
         
           40  illuminator assembly 
           41  plastic portion 
           43  metal body 
           44  illuminator assemblage 
           45  contact pin 
           47  contact socket 
           48  grippable-strain relief 
           50  transformer 
           51  insulator 
           52  electrical cable 
           53  lead wire 
           54  electrical cable 
           55  wing band 
           56  illuminator switch assembly 
           58  plug 
           59  plug 
           60  miniature incandescent lamp 
           61  wire splice 
           62  electrical conductors 
           63  assembly housing 
           64  lamp housing 
           65  cover 
           66  distal end—lamp 
           67  rocker switch 
           69  flexible boot 
           70  distal end—lamp housing 
           71  fasteners 
           73  cable 
           74  lamp leads 
           75  molded body 
           78  filament—lamp 
           80  male connector pins 
           82  lamp envelope 
           83  wire band 
           86  contact 
           90  proximal end 
           94  insulator 
           98  O-ring 
           102  circumferential slot 
           106  sleeve 
           108  bond 
           200  miniature incandescent lamp 
           202  adhesive 
           204  housing 
           212  electrical leads 
           216  contact 
           220  distal end—lamp 
           224  distal end—housing 
           300  disposable vaginal speculum 
           304  fixed blade member 
           308  movable blade member 
           312  slide member 
           316  hollow leg 
           320  forked upper end 
           324  lever portion 
           332  lower tongue 
           336  slot 
       
    
     While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawings, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.