Title of Invention

IMPROVED LARYNGOSCOPE BULB

Abstract

The present invention relates to an improved light source for laryngoscopes, said improvement consisting of a bulb with injection-molded casing which has reduced heating, is autoclavable, low-cost, easier to manufacture and can be fitted into existing metallic laryngoscope blades in a removable manner without any modification of the circuit whatsoever. This has been made possible by the presence of two critically positioned holes in the casing which provide exit points for the bulb wires, enabling them to come into contact with metallic portions of existing conventional laryngoscope blades, thus leading to completion of the circuit and functioning of the bulb In addition, the height ratio of the barrel and screw threaded portions is also reduced from 3:1 to 2:1 to ensure greater stability and easier fitting of the bulb.

Full Text

Field of the Invention: The present invention relates to an improved laryngoscope bulb. More specifically it pertains to an improved plastic laryngoscope bulb capable of being attached in a removable manner to conventional laryngoscopes without any modification of the electrical circuit whatsoever. Prior Art As is known and explained, e.g., in U.S. Pat. No. 3,766,909, a laryngoscope is a type of device for assisting in the observation of the oral cavity, particularly the laryngeal areas. It is employed for examining the larynx and serves as an aid for inserting an end tracheal tube through the larynx into the trachea during anesthesia. In order to obtain accurate placement, the instrument must be capable of restraining the patient's tongue, while engaging the epiglottis to reveal the larynx for visual observation. These functions are greatly aided by the use of a light source e.g. an electric bulb, present in the laryngoscope blade for producing localized illumination of the area being examined. Furthermore, as known and explained e.g., in U.S. Pat. No. 4,557,256, laryngoscopes generally comprise a blade and a cooperating handle which are connected together in a generally L-shaped configuration. The blade is made primarily of metal, generally surgical steel while the handle is also made of metal generally brass and houses a power source which powers a light source viz. a metallic electric bulb attached to a socket fixed to the blade portion. The switch for activating the light is usually positioned immediately adjacent to the light bulb and is operated by the blade when it is connected onto the handle. The light from the bulb passes through a clear light conductor to the distal end of the blade, to illuminate the patient's mouth and larynx during the examination thereof by medical personnel. To prevent the patient's tongue from obstructing the visual examination of the larynx, the surface of the blade adjacent to the handle is pressed against the tongue and mandible of a patient in a supine position. As more fully explained, e.g., in U.S. Pat. No. 4,878,486 the human body tends to function somewhat irregularly under the influence of anesthesia. The air passageway may close up, and stomach acid may enter the lungs. To avoid such a situation and protect the lungs from stomach acid, an endotracheal tube is normally inserted into the patient's air passageway with the aid of a device which is typically used to examine the larynx, namely a laryngoscope. A conventional laryngoscope comprises a handle of cylindrical shape with a detachable, elongate blade. The blade has a light source located adjacent its outer end to assist in viewing the larynx, and a rounded tip to help move the epiglottis to facilitate the insertion of an endotracheal tube without undue trauma to the patient's throat. In early laryngoscope blades, the light source was supported by and formed part of the blade at a position near the tip of the blade. An example of this type of arrangement is set forth in U.S Pat. Nos. 3,426,749 and 3,856,001 Unfortunately, it was found that the bulb on the blade generated heat and this caused discomfort to the patient. In addition, the blade had to be cleaned and sterilized and this procedure sometimes damaged the bulb. To overcome this problem, use of fibre optics was proposed in the blades, whereby light source was in the handle and light was carried to the blade by means of light conducting fibers. Thus the problem of heating and damage to bulb during sterilizaton was overcome Such an arrangement has been described in U.S. Pat. No 4,273,112 In this type arrangement, the bulb is not located in the blade, but in the handle which is connected by a latching mechanism to the laryngoscope blade. In another improvement, accentuated by fears of cross-contamination, laryngoscope blades were made of plastic to render them disposable or routine autoclaving of existing stainless steel blades was made mandatory. Accordingly, there was felt to be a demand in the medical field for disposable covers for laryngoscopes or for disposable blades, and many recent patents have been directed to this problem Thus, e.g., U.S. Pat. Nos. 3,426,749; 4.583,527; 4,579,108; 4,878,486; 4,884,558; 4,972,825 and 5,065,738 all attempt to solve the aforementioned sterility problem by providing disposable covers or sheaths for the standard laryngoscope blade. Similarly, U.S. Pat. Nos. 3,826,248; 3,598,113; 3,766,909; 4,037,588; 4,406,280; 4,570,614; 4,565,187; 4,406,280 and 4,930,495 provide different types of disposable blades for use in laryngoscopy. None of the patents as described above have been filed in India. Moreover, there is no record of any existing Indian Patents w.r.t. present invention. Despite the existence of these patents and their proposed solutions, 99% of the laryngoscopes used remain of the conventional figuration with a standard metal handle and metal blade. The reasons for this are not far to seek. Disposable sheaths or covers not only remove light intensity, but add a non-rigid component to the laryngoscope blade Moreover, while many of the proposed disposable blades are inexpensive in themselves being made of plastic, they are proposed for use in combination with a specially-designed handle and cannot be used with existing handles. US patent no 5,879,304 describes a disposable blade which can be used with existing handles in conformity with International Standard ISO-7376-1. It has a bulb permanently fixed in a cavity. However, quite a few hospitals with existing stock of stainless steel blades, prefer to autoclave and reuse the blades. Moreover, owing to increasing environmental concerns about pollution caused by disposables, some hospitals may choose not to adopt disposable plastic blades and instead use the conventional metallic blades which can be reused simply by autoclaving. Thus, despite the existence of several innovative laryngoscopes aimed at improving the quality of healthcare and also lowering -costs, metallic blades of conventional type still remain immensely popular owing to reasons discussed above. This is despite the limitations and disadvantages of metallic bulbs which act as the light source in such blades In general, some of the disadvantages associated with metallic casing of bulbs are:  Gets heated during operation of bulb, which is not desirable as instrument is in contact with soft tissues  Enhances cost of the bulb, as brass is expensive. j~  Slows production as not only machining of metal but electroplating of the finished metallic casing is also required.  Moreover, owing to variations during machining process, bulbs may show slight variation in size w.r.t outer diameter and height. These slight variations can cause problems in fixing of the bulb into the laryngoscope blade owing to small size of available space. A bulb which is non-heating, autoclavable and can be attached in a removable manner to existing laryngoscope blades without any modification of the circuit thus has considerable appeal. However, no such bulb has been described either in existing patents nor is it commercially available. Attempts have been made to overcome problems associated with metallic bulbs by providing bulbs with injection-molded plastic casing. Despite the advantages of low-cost, faster and more precise production and also better heat insulation offered by such injection moulded bulb casings, these have not become popular. A careful analysis of the products by the inventors reveals that there exist major drawbacks with respect to the improved non-metallic bulbs which are commercially available.  Existing commercially available laryngoscope bulbs with injection molded casing (PROACT USA) require special wiring of the blade to accommodate the injection molded bulb and provide necessary conductivity for completing the electrical circuit.  They cannot be fitted into existing laryngoscope blades of conventional type.  The bulbs are not removable but are permanently fixed to the blade leading to complete wastage of entire blade in event of failure or breakage of the bulb.  Moreover, bulbs are used in metallic blades which are of single use and the casing is not autoclavable. Thus, none of the bulbs proposed in patents or commercially available are able to meet the requirements of being non-heating, injection-molded and capable of being attached in a removable manner, to existing laryngoscope blades of conventional type viz. those which are detachably connectable to a hook-on-type conventional metallic laryngoscope handle in conformity with International Standard ISO-7376-1. With the above state of the art in mind, according to the present invention there is now provided an improved light source for laryngoscopes comprising a bulb with non-metallic, injection molded casing, capable of being removably fitted into existing metallic laryngoscope blades of conventional type viz. those which are detachably connectable to a hook-on-type conventional metallic laryngoscope handle in conformity with International Standard ISO-7376-1. The injection molded casing can be of any tough thermoplastic material such as ABS, polycarbonate, polypropylene or even a mixture of two plastics, the choice of material being determined by the fact whether the blade is of single use or reusable and subject to autoclaving, as not all plastics are autoclavable Polypropylene offers the advantage of high thermal resistance, autoclavability and also flexibility enabling easy and convenient assembly of the bulb. The improved bulb having non-metallic injection molded casing has a rating of about 2.5-3V and 150-250 mAmp. Preferably, said bulb is an incandescent, krypton or other gas-filled bulb providing illumination of at least 650 lux Particular advantages offered by the present invention are:  Considerably reduced heating as compared to metallic bulbs  Faster production  Reduced costs since production steps and accessories are less e.g. there is no need for electroplating and some non-conducting parts are also eliminated  Easier and simpler assembly, not requiring skilled labor OBJECTS OF THE PRESENT INVENTION An object of the present invention is to provide an improved injection molded laryngoscope bulb which has considerably reduced heating, is autoclavable, low-cost, easier to manufacture and can be fitted into existing metallic laryngoscope blades of conventional type, in a removable manner without any modification of the electrical circuit whatsoever. Another object of the present invention is to provide a bulb which can be fitted rapidly into the metallic laryngoscope blades for commercial production, using a tool. For this, outer surface of casing is cylindrical with flattened sides, so that tool can be fitted from the top to enable quick and easy tightening. It is also an object of the present invention to provide an improved bulb which is easy to fit and remove with fingers. This is accomplished by reducing height of injection molded casing by 1/3rd that of a conventional laryngoscope bulb with metallic casing i.e. to 8 mm from 12 mm Another object of the present invention is to provide a bulb with a safety feature viz inability to function in event of a loose fit. Bulb lights up only when it is fully screwed into the metallic socket, as conductive point enabling completion of the circuit is at outer middle edge of the bulb. Yet another object of the present invention is to provide a bulb with an injection molded casing (which is a natural heat insulator) so that the disadvantages of heating associated with metallic casings, are overcome. It is also an object of the present invention to provide an improved bulb which can be simply and inexpensively assembled by unskilled labor, without the need for specialized tools or machinery. Lastly, it is an object of the present invention to provide a bulb with a smooth outer surface which is easy to clean and disinfect, unlike in metallic casings where the ridges on the surface trap blood particles/bacteria which are very difficult to remove. SUMMARY The present invention provides a simple, low-cost light source with reduced heating, for laryngoscopes More particularly, the invention pertains to a light source consisting of an electric bulb with injection molded casing which can be removably attached to metallic laryngoscope blades of conventional type without any modification of the electrical circuit whatsoever, even though the injection molded casing of present invention is non-conducting. This has been made possible by incorporation within the casing itself, of two critically positioned holes which serve as exit points for the electrical wires of the bulb, representing the positive and negative terminals respectively. The wire exiting from the lateral hole is coiled to a length of 3-5mm at the juncture of upper non-threaded and lower screw-threaded part of the bulb, so that when the bulb is tightened the circuit is completed by the wire coming into contact with the metallic portion of the laryngoscope blade via the metallic socket into which the bulb is being tightened. Similarly, the wire exiting from the central hole comes into contact with the second terminal located at base of the metallic socket welded to the laryngoscope blade These and other objects, features and advantages of the present invention however will be more fully realized and understood from the following detailed description, when taken in conjunction with the accompanying drawings. It is stressed that particulars shown are by way of example and illustrative purposes only. No attempt is made to show structural details in more detail than is necessary for a , An improved laryngoscope bulb characterized in that it consists of a) a plastic casing made of two parts- lower screw threaded part with two holes and an upper barrel part b) a light emitting assembly housed in the upper baser part of said easing wherein the positive of negative electrical connecting users of the said light assembly escit through the holes in the said casing and the said improved laryngoscope bulb is capable of being screw fitted in a detachable manner, into the sachets of a hath-on-type conventional laryngoscope blade. fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practise, DESCRIPTION OF FIGURES FIG. 1 A is a view in perspective of a known prior art conventional laryngoscope consisting of a metallic blade A and a metallic handle B containing electric batteries B1 and B2. The blade A has a small metallic electric bulb CM fixed in socket D soldered to the body of the metal blade. FIG. 1 B is an enlarged view of the electric bulb CM fitted in the socket D. The electric bulb CM consists of three parts- an upper glass part G, fitted in a metallic shell consisting of upper U shaped, cylindrical part UM and a lower screw threaded part SM . The bulb has two exit wires, W1.and W2 which are in contact with the positive and negative terminals of the electric batteries, respectively through appropriate connections as provided in the metallic blade FIG. 2 is an enlarged view of the improved, plastic laryngoscope bulb CP, showing position of holes h1 and h2 in cylindrical plastic casing UP. Plastic casing has two parts, a screw threaded lower portion SP and an upper smooth hollow portion UP housing the glass portion of the electric bulb G. The holes in the casing, h1 and h2 provide exit points for the wires W1 and W2 of the bulb which connect to corresponding positive and negative terminals of the battery respectively through appropriate connections as provided in the metallic blade. FIG. 3 is an enlarged view of the improved plastic laryngoscope bulb CP fixed in metallic socket D of conventional laryngoscope blade A. Bulb wires W1 and W2 exit from the plastic casing CP through the holes h1 and h2 respectively . Since body of the improved plastic laryngoscope bulb is non-conducting, W2 cannot terminate in body of casing as in metal bulb and appropriate exit point h2 is specially provided in casing of improved bulb. Wire W2 exiting from the hole h2 is coiled 2-3mm along the junction of the upper portion UP and lower screw threaded portion SP, so that when bulb is tightened circuit is completed by contact of the bulb wire W2 with the metallic socket D. Like reference alphabets throughout the various views of the drawings are intended to designate the same elements DESCRIPTION OF INVENTION w.r.t. DRAWINGS With reference to Fig. 1A, a laryngoscope generally comprises, a blade A secured to a cylindrical metal handle B in a generally L-shaped configuration, the blade A being of conventional metallic variety which is detachabiy connectable to a hook-on-type conventional metallic handle in conformity with International Standard ISO-7376-1. The instrument is utilized to depress a patient's tongue and mandible to expose the patient's larynx during an examination thereof or the insertion of an endotracheal tube The blade A has a cylindrical, metallic socket D soldered to it, into which a light source e.g a metallic electric bulb CM can be screwed in. The handle B generally houses two batteries B1 and B2 of 1 5 V each for powering the light source CM through appropriate connections/circuit The light bulb CM has two depending electrode means, W1 and W2 which connect to the positive and negative terminals of the batteries respectively, when the blade is in operating position as shown in Fig.1A. The light source CM is usually a small glass bulb/incandescent lamp comprising three parts- an upper glass part G, a middle hollow cylindrical metal casing part UM and a lower screw threaded part SM. The metal casing has ridges on outer surface to ensure proper gripping with fingers during fixing and is electroplated with nickel or chromium to prevent spoilage of metallic surface due to oxidation. The bulb CM is fixed to the laryngoscope blade by screwing into a bulb holder/socket D attached to the blade and its conductivity and functionality is maintained by connection of the two exiting wires of the bulb W1 and W2 to separate electrical poles of the batteries designated as positive and negative respectively (Fig.18). One wire W1 passes vertically through the metallic casing, exits from the center of the screw threaded lower part of the casing and is in contact with the positive terminal of the batteries through appropriate wiring in the screw-threaded metallic socket fixed to the laryngoscope blade. The exit point of this wire is surrounded by a small ring of non-conducting material e.g. teflon, plastic etc. to prevent short-circuiting. The second wire W2 of the bulb terminates into the metallic casing itself, which is in contact with the negative terminal of the batteries via conductivity offered by the metallic body of the bulb and also metallic holder into which the bulb fits. Thus, the metallic casing of the bulb plays an important part in functioning of the bulbs by providing the negative pole of electrical conductivity and completing the electrical circuit Barrel size (length) of the commercially available metallic bulb casings is 12-13mm (UM) in addition to a screw-threaded portion (SM) of 4-5 mm. Thus total casing length of the metallic bulb CM is 16-18 mm. Outer diameter of the upper portion of casing is 5 mm, while that of lower screw threaded portion is 4mm. Bulbs fixed to pediatric blades are still smaller having a casing length of only 9 mm with additional screw threaded portion of length 3.5-4.5 mm. Thus total casing length is 12.5-13.5 mm. with an outer diameter of 4mm of upper portion and 3mm of lower screw threaded portion Dimensions are critical owing to specific sizes of the sockets and. cavities where the bulbs are going to be fixed. In the improved light source as proposed in the present invention, the metallic conducting casing of the bulb CM is replaced by an injection molded, plastic nonconducting casing CP (Fig.2). The plastic casing has two parts- an upper u-shaped hollow part (UP, Fig. 2) having dimensions 8mm x 5mm x 4mm (length x outer diameter x inner diameter mm) and a lower screw-threaded solid part (SP, Fig. 2) having dimensions 4mm x 4 mm (length x outer diameter). Glass portion of bulb (G, Fig. 2) fits snugly into hollow part UP of the plastic casing 4' merely by pushing in, thus eliminating need for any special tooling, machines or skilled labor. Overall barrel length of the injection molded casing is also reduced by 1/3rd to facilitate easy removal and attachment of bulb in existing laryngoscope blades In contrast to existing barrel length of 12 mm of the metallic casing, the injection molded casing of improved bulb has a barrel length of 8 mm. In case of existing electric bulbs with metallic casing, the metallic body itself acts as a conductor and has one bulb wire W2 terminating into the body itself, allowing the circuit to be completed with the negative terminal of the batteries. However, this is not possible in present invention since body of the improved plastic laryngoscope bulb is non-conducting because of which W2 cannot terminate in body of casing as in metal bulb. Accordingly, for maintaining functionality of the bulb, the casing has two critically positioned holes- a lateral hole (h2, Fig.2) at the juncture of the upper U-shaped part with lower screw-threaded part and a central hole (hi, Fig.2) at the tip of the screw threaded part. The electric bulb is pushed into the hollow cavity of the casing. One wire (W1, Fig.2) of the bulb is passed out through the central hole hi of the injection molded casing and locked in position either by bending at right angles or by pushing a metallic pin/rivet through the hole. This wire (hi) provides the positive electrical contact The second wire (W2) is exited through the lateral hole h2 and rolled 2-3mm along the ridge at junction of upper and lower parts of casing This wire provides the negative electrical contact When the improved bulb is screwed into the bulb holding socket of a conventional laryngoscope blade, the positive contact touches the electrical contact at the bottom of the socket. When the bulb is fully tightened, the small piece of wire W2 (negative contact) exiting from the lateral hole h2 and curved along the periphery of the improved bulb, comes into contact with the rim of the metallic socket into which bulb is being fitted, thus completing the circuit and allowing the bulb to function (Fig.3). An added advantage of this feature is that unless the bulb is fully tightened, it will not function, thus eliminating any chances of accident caused by a loosely fitting bulb. The outer surface of injection molded casing is smooth and cylindrical with flattened sides, enabling quick and easy tightening with tool during production besides offering an improved surface for cleaning during use. In case of surface with ridges as in case of metallic casing, effective cleaning after use becomes practically difficult as blood, mucus, particles etc. get trapped in the ridges and are extremely difficult to remove In a preferred embodiment, the positive terminal of bulb (W1) can have a metallic washer attached to it at exit point, to facilitate electrical contact. Similarly, negative terminal of bulb (W2), can be soldered to a metallic washer at exit point to facilitate contact with metallic socket. In a second preferred embodiment, the injection molded casing UP can be made of ABS which can be electroplated to provide a surface with metallic finish so as to make it indistinguishable from bulbs with metallic casings. In another embodiment, the injection molded casing UP can be made of polypropylene enabling the bulb to be autodaved just like bulbs with metallic casing. In a further embodiment, the bulb is a tungsten wire filament-vacuum bulb providing the desired level of illumination viz. 650 lux. In yet another embodiment, the brass pin/rivet being fixed in plastic casing through hole h1 and coming into contact with the wire providing positive electrical contact is electroplated with nickel or chromium to prevent oxidation of contact point, thus ensuring reliable functioning of the bulb. In all embodiments, positive and negative electrode conducting wires extend from the bulb The above description is for illustrative purposes only and should not be construed as a limitation of the invention One skilled in the art may be able to make suitable variations, substitutions and changes in the ingredients and parameters, without departing from the scope of the invention. CLAIMS We claim: 1. An improved laryngoscope bulb characterized in that it consists of a) a plastic casing made of two parts- lower screw-threaded part with two holes and an upper barrel part b) a light emitting assembly housed in the upper barrel part of said casing wherein the positive and negative electrical connecting wires of the said light assembly exit through the holes in the said casing and the said improved laryngoscope bulb is capable of being screw- fitted in a detachable manner, into the socket of a hook-on-type conventional laryngoscope blade. 2. An improved laryngoscope bulb as claimed in claim 1 wherein said casing is injection molded plastic and comprises of autoclavable material such as polypropylene, polyethylene or like plastics. 3. An improved laryngoscope bulb as claimed in claim 1 wherein lower screw threaded portion of said casing has optimal dimensions (length x outer diameter) of 4mm x 4mm for adult and 4mm x 3mm for pediatric laryngoscope blades and an upper hollow cylindrical part of optimal dimensions 8mm x 5mm for adult and 8mm x 4mm for pediatric laryngoscope blades respectively, the minimum thickness of the walls of the casing being 1mm and ratio of screw threaded portion to upper barrel portion of said casing is 1:2. 4 An improved laryngoscope bulb as claimed in claim 1, wherein one of the holes in the said casing is positioned laterally at junction of the screw threaded portion with barrel portion and second hole is positioned centrally at tip of screw threaded portion. 5 An improved laryngoscope bulb according to claims 1 and 4 wherein the lateral and central holes provide exit to the conducting wires of light assembly, which connect to negative and positive terminals respectively of battery housed in the laryngoscope handle to which the laryngoscope blade is attached. 6, An improved laryngoscope bulb according to claims 1,2,3,4 and 5 wherein necessary electrical contact points of the bulb for completing the circuit and allowing the bulb to function are provided by wires exiting from lateral and central holes present in plastic casing of the bulb, such that when the bulb is fully screwed into socket of existing conventional metallic laryngoscope blades, the exiting wire from lateral hole comes into contact with metallic edge of socket of blade corresponding to negative terminal, while the exiting wire from central hole comes into contact with metallic pin at base of socket corresponding to positive terminal, thus leading to completion of circuit and allowing bulb to function just like a normal metallic bulb. 7. An improved laryngoscope bulb of claim 1 wherein outer surface of the plastic casing is rough textured to enable gripping for fitting of bulb into socket of the laryngoscope blade. 8 An improved laryngoscope bulb of claim 1 wherein the light emitting assembly housed in the plastic casing of the bulb is a krypton or any other gas filled incandescent glass bead having an optimal rating of 2.5-3Volts, 0.1-0.3 Amps illumination of at least 650 lux and an operating life of several hours on interrupted use or at least 10 minutes continuous use. An improved laryngoscope bulb substantially as herein described with respect to the description and figures number 2 and 3.

Documents:

438-del-2004-abstract.pdf

438-del-2004-claims.pdf

438-del-2004-correspondence-others.pdf

438-del-2004-correspondence-po.pdf

438-del-2004-description (complete).pdf

438-del-2004-form-1.pdf

438-del-2004-form-19.pdf

438-del-2004-form-2.pdf

438-del-2004-form-3.pdf

438-del-2004-form-5.pdf