Abstract:
A pen light bulb which is self aligning in conventional pen light flashlights is disclosed. Applicable pen light flashlights rely upon pressure bearing retention of the bulb therein. A focusing lens protective element of the pen light bulb has various features which provide for a more stable seating surface thereon to contact the housing of the pen light flashlight. These features provide for the axis of projection of the beam of light from the bulb to match, or nearly match, a central axis of the pen light flashlight. A wider and larger spring contact surface on a circular base of the housing of the pen light bulb provides for a truer application of pressure by a spring to the pen light bulb to assist in proper alignment within conventional pen light flashlights.

Description:
BACKGROUND 
     1. Field of the Invention 
     Generally, the invention relates to small light bulbs. More specifically, the invention relates to such light bulbs suitable for use in conventionally known pen light flashlights where a portion of the bulb proper acts to focus and direct a beam of light utilizing optical focusing qualities contained entirely on the bulb. 
     2. Description of the Prior Art 
     Pen light flashlights produce a beam of light wherein the bulb contains structures which focus the produced light into the desired beam. The discussion of the prior art will be limited to these types of flashlight, and applicable bulbs which are sometimes referred to as lamps. 
     There exist three mounting methods for pen light bulbs within conventionally known pen light flashlights. A first method of mounting the bulb within the pen light flashlight involves providing threads within the housing of the pen light flashlight which receive threads positioned on the bulb. This type of mounting generally provides for proper and true alignment of the bulb within the pen light flashlight wherein the axis of the beam of produced light aligns with a central axis of the pen light flashlight. One major disadvantage of this type of pen light flashlight involves an increase in production costs associated with fairly precise production of the threads within the housing of the pen light flashlight. A second method of mounting the bulb within the pen light flashlight involves utilization of the typical mounting method used in conventional collimating flashlights wherein a relatively wide rim on the bulb is held between two securement structures of the pen light flashlight. Typically these two securement structures will involve opposing threads which cooperate to trap the bulb between two radially disposed trapping surfaces. One major disadvantage of this type of pen light flashlight also involves an increase in production costs associated with fairly precise production of a set of threads within the housing of the pen light flashlight and fairly precise production of a ring member with a set of threads thereon. A third method of mounting the bulb within the pen light flashlight involves retention of the bulb utilizing a pressure bearing contact of the bulb against a portion of the housing of the pen light flashlight. Pen light flashlights which use this pressure bearing method of mounting have the advantage of being inexpensive to manufacture when compared to pen light flashlights which utilize either of the other methods of mounting of the bulb. 
     The pressure bearing contact method is the method applicable to the present invention and typically involves providing a radially disposed inwardly facing seating surface situated about a terminal end aperture upon which a transparent end of the bulb rests with a focusing portion of the bulb extending outward through the aperture. A spring member typically applies the pressure. This spring is either positioned between the bulb and a battery or behind the battery, or batteries, with the battery in contact with the rearward end of the bulb. 
     The pressure bearing contact method has several disadvantages when conventionally known pen light bulbs are employed. Pen light bulbs typically do not have wide lips on the metallic housing adjacent the transparent protective cover. Therefore the pressure bearing contact must occur against the transparent protective cover. These conventionally known bulbs are designed with a fairly long narrow portion at the outward extent of the transparent protective cover where the optical focusing portion is located. This contour arrangement provides for an extremely unstable mounting of the bulb wherein tipping may easily occur. Additionally, the base of conventionally known pen light bulbs have a relatively small diametric measurement. This small size of the base is even more pronounced when threads are positioned on the pen light bulb. This narrow base tends to increase the tendency of the bulb to tip out of alignment with the central axis of the pen light flashlight. This tipping tendency is even more pronounced when the spring is positioned against the bulb, which is the most common placement position. 
     As can be seen various attempts have been made to provide for a pen light bulb which may be utilized within conventionally known pen light flashlights. Typically, manufacturers are willing to accept that the axis of the beam of projected light does not match the central axis of the pen light flashlight proper. Previously, it has been necessary to increase production cost by utilizing a more complicated housing design in order to eliminate the out of alignment beam of projected light. These attempts have been less efficient than desired. As such, it may be appreciated that there continues to be a need for a pen light bulb which may be installed into existing pen light flashlight designs where a truer alignment occurs than that previously possible with conventional pen light bulbs. The present invention substantially fulfills these needs. 
     SUMMARY 
     In view of the foregoing disadvantages inherent in the known types of pen light bulbs, your applicants have devised a method of providing for a proper alignment of a pen light bulb in conventional pen light flashlights wherein the configuration of the bulb provides for the proper alignment. A self aligning pen light bulb produces a beam of light in response to an introduction of a power flow. The self aligning pen light bulb has a housing, having a first power coupling thereon, a second power coupling, an insulator, a filament and a focusing lens protective element. The housing has a circular body and a circular base. The circular body has an upper extent having an opening thereat. The circular base is positioned distal from the upper extent of the circular body. The circular base is generally planar with an aperture therethrough. The housing has an interior and an exterior with at least a portion of the exterior forming the first power coupling which provides for a passage of the power flow from the exterior to the interior. The housing also has a central axis through the interior of the housing and extending from a central position of the circular base to a central position of the opening at the upper extent. The second power coupling is positioned to extend from the exterior of the circular base and generally aligned with the central axis of the housing. The second power coupling provides for a passage of the power flow to the interior of the housing. The insulator is positioned between the second power coupling and the exterior of the circular base to prevent passage of the power flow between the second power coupling and the exterior of the housing. The filament is in communication with the first power coupling and the second power coupling. The filament produces a light during the introduction of the power flow. The focusing lens protective element has a focusing portion, an upper tapered portion, a lower tapered portion and a mounting portion. The focusing portion has optical qualities to provide for a focusing of the light produced by the filament. The focusing portion is radially disposed about the central axis of the housing distal from the housing. The upper tapered portion is radially disposed about the central axis of the housing and extends from the focusing portion toward the housing. The upper tapered portion has an angle of taper extending outward from the focusing portion toward the housing. The lower tapered portion is radially disposed about the central axis of the housing and extends from the upper tapered portion toward the housing. The lower tapered portion has an angle of taper extending outward from the upper tapered portion toward the housing. The angle of taper of the lower tapered portion is significantly greater than the angle of taper of the upper tapered portion. The mounting portion extends from the lower tapered portion into the interior of the housing. 
     My invention resides not in any one of these features per se, but rather in the particular combinations of them herein disclosed and it is distinguished from the prior art in these particular combinations of these structures for the functions specified. 
     There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. Those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     It is therefore a primary object of the present invention to provide for a self aligning pen light bulb which may be employed in existing pen light flashlights. 
     Other objects include; 
     a) to provide for a better seating surface on the transparent protective element of the pen light bulb than that which exists on conventional pen light bulbs. 
     b) to provide for a wider spring contact surface on the circular base of the pen light bulb than that which exists on conventional pen light bulbs. 
     c) to provide for a spring contact surface on the circular base of the pen light bulb with a significantly greater area than that which exists on conventional pen light bulbs. 
     d) to provide for a wider focusing portion on the transparent protective element of the pen light bulb than that which exists on conventional pen light bulbs. 
     e) to provide for a housing having a circular body with a larger diametric measurement than that which exists on conventional pen light bulbs. 
     f) to provide for easier manufacture of the pen light bulb by providing for a larger interior of the circular body of the pen light bulb than that which exists on conventional pen light bulbs. 
     g) to provide for an upper tapered portion and a lower tapered portion on the focusing lens protective element with generally equal lengths along the central axis of the pen light bulb. 
     These together with other objects of the invention, along with the various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated the preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein; 
     FIG. 1 is an elevational view of a self aligning pen light bulb. 
     FIG. 2 is a bottom plan view of the self aligning pen light bulb shown in FIG.  1 . 
     FIG. 3 is an enlarged partial view as taken from FIG.  1 . 
     FIG. 4 is an elevational view of the self aligning pen light bulb shown in FIG. 1 with various portions cutaway to reveal the internal arrangement. 
     FIG. 5 is a bottom plan view of a spring and labeled as ‘Prior Art’. 
     FIG. 6 is an elevational view of a conventional pen light bulb and labeled as ‘Prior Art’. 
     FIG. 7 is a bottom plan view of the conventional pen light bulb shown in FIG.  6  and labeled as ‘Prior Art’. 
     FIG. 8 is an enlarged partial view as taken from FIG.  6  and labeled as ‘Prior Art’. 
     FIG. 9 is an elevational view of an upper portion of a pen light flashlight having the self aligning pen light bulb shown in FIG. 1 installed therein. 
     FIG. 10 is an elevational view of the upper portion of the pen light flashlight shown in FIG. 9 having the conventional pen light bulb shown in FIG. 4 installed therein and labeled as ‘Prior Art’. 
     FIG. 11 is a sectional view of the upper portion of the pen light flashlight shown in FIG. 9 with part of the housing cutaway. 
     FIG. 12 is a sectional view of the upper portion of the pen light flashlight shown in FIG. 10 with part of the housing cutaway and labeled as ‘Prior Art’. 
     FIG. 13 is an exploded elevational sectional view of a pen light flashlight having the self aligning pen light bulb shown in FIG. 1 installed therein. 
    
    
     DESCRIPTION 
     Many different pen light bulbs having features of the present invention are possible. The following description describes the preferred embodiment of select features of those bulbs. These features may be deployed in various combinations to arrive at various desired working configurations of pen light bulbs. 
     Reference is hereafter made to the drawings where like reference numerals refer to like parts throughout the various views. 
     Self Aligning Bulb Construction 
     FIG.  1  through FIG. 4 depict a self aligning pen light bulb  20 , or portions thereof, having features of the present invention. Self aligning pen light bulb  20  has a glass envelope  22 , a housing  24  and a power coupling  26 . Power coupling  26  is separated from housing  24  by an insulator  28 . Glass envelope  22  rests within housing  24  and is secured therein by material of insulator  28  which preferably extends into housing  24  to surround a terminal end  30  of glass envelope  22 . Glass envelope  22  is a sealed unit having a first electric lead  32  and a second electric lead  34  extending from terminal end  30  thereof, see FIG.  4 . First electric lead  32  connects to an interior  36  of housing  24 . Second electric lead  34  connects to power coupling  26 . 
     Glass envelope  22  has positioned therein a first power pole  38  connected to first electric lead  32  and a second power pole  40  connected to second electric lead  34 . A spacing insulator  42  retains first power pole  38  and second power pole  40  in spaced relationship within glass envelope  22 . A filament  44  is connected to span the gap between first power pole  38  and second power pole  40 . Filament  44  produces a light when power passes therethrough. Glass envelope  22  is a continuous sealed transparent member and has a focusing portion  46 , an upper tapered portion  48 , a lower tapered portion  50  and a mounting portion  52 . 
     Focusing portion  46  is radially disposed and has a maximum thickness  54  and a diametric width  56 . Focusing portion  46  further has a radius  58  at an exterior  60  of glass envelope  22 . Focusing portion  46  forms an optical focusing lens  62  to focus light produced by filament  44  into a beam of light  64 , see FIG. 9, having an axis of projection  66 . Preferably maximum thickness  54  of focusing portion  46  is between one and eight tenths (1.8) millimeters and one and nine tenths (1.9) millimeters while diametric width  56  of focusing portion  46  is between six (6.0) millimeters and six and two tenths (6.2) millimeters while radius  58  of focusing portion  46  is between three and thirty five hundredths (3.35) millimeters and three and fifty five hundredths (3.55) millimeters. More preferably maximum thickness  54  of focusing portion  46  is one and eighty five hundredths (1.85) millimeters while diametric width  56  of focusing portion  46  is six and one tenth (6.1) millimeters while radius  58  of focusing portion  46  is three and forty five hundredths (3.45) millimeters. 
     Upper tapered portion  48  has a thin wall construction and is radially disposed to extend downward from focusing portion  46  a depth  68 . Upper tapered portion  48  has an angle of offset  70 , see FIG.  3 . Preferably depth  68  of upper tapered portion  48  is between two and two tenths (2.2) millimeters and two and four tenths (2.4) millimeters while angle of offset  70  of upper tapered portion  48  is between seven (7.0) degrees and eight (8.0) degrees. More preferably depth  68  of upper tapered portion  48  is two and three tenths (2.3) millimeters while angle of offset  70  of upper tapered portion  48  is seven and one half (7.5) degrees. 
     Lower tapered portion  50  has a thin wall construction and is radially disposed to extend downward from upper tapered portion  48  a depth  72 . A transition  74  exists between upper tapered portion  48  and lower tapered portion  50 . Lower tapered portion  50  has an angle of offset  76 , see FIG. 3, which is significantly greater than angle of offset  70  of upper tapered portion  48 . Ideally during mounting within a pen flashlight contact between self aligning pen light bulb  20  and the body of the pen flashlight will occur at lower tapered portion  50  with a portion of lower tapered portion  50  forming a seating surface  78 , see FIG.  3  and FIG.  11 . Preferably depth  72  of lower tapered portion  50  is between two and one tenth (2.1) millimeters and two and three tenths (2.3) millimeters while angle of offset  76  of lower tapered portion  50  is between twenty five (25.0) degrees and twenty seven (27.0) degrees. More preferably depth  72  of lower tapered portion  50  is two and two tenths (2.2) millimeters while angle of offset  76  of lower tapered portion  50  is twenty six (26.0) degrees. 
     Mounting portion  52  generally has a thin wall construction and is radially disposed to extend downward from lower tapered portion  50 . Mounting portion  52  is sealed at terminal end  30  during manufacture of glass envelope  22 . 
     Housing  24  has a circular body  80  and a circular base  82 . Housing  24  further has interior  36 , an exterior  84  and a central axis  86  extending therethrough. Circular base  82  has an aperture therethrough to which second electric lead  34  passes for connection to power coupling  26 . Housing  24  preferably is constructed of a conductive material. First electric lead  32  attaches to interior  36  of housing  24 , see FIG.  4 . Circular body  80  has an upper extent  88  distal from circular base  82 . Upper extent  88  radially defines an opening  90  which is closed by glass envelope  22 . Insulator  28  prevents contact of second electric lead  34  with housing  24 . Interior  36  of circular body  80  has a diameter  92 , see FIG.  4 . Preferably exterior  84  of circular body  80  is smooth. Preferably diameter  92  of interior  36  is between nine (9.0) millimeters and nine and two tenths (9.2) millimeters. More preferably diameter  92  of interior  36  is nine and one tenth (9.1) millimeters. 
     Circular base  82  of housing  24  is generally flat with a transition  94 , which preferably is slightly rounded, between circular base  82  and circular body  80 . A spring contact surface  96  is formed by circular base  82  outside of insulator  28 . Spring contact surface  96  has an outer diametric measurement  98 , an inner diametric measurement  100  and an area  102 . Outer diametric measurement  98  generally matches a diameter of circular body  80  adjacent circular base  82 . In practice, when the spring is positioned between the bulb and the battery, a spring  104 , see FIG.  5  and FIG.  12  and labeled as ‘Prior Art’, ideally will rest completely on spring contact surface  96 . Preferably outer diametric measurement  98  of spring contact surface  96  is between nine (9.0) millimeters and ten (10.0) millimeters while inner diametric measurement  100  of spring contact surface  96  is between six (6.0) millimeters and six and one half (6.5) millimeters with area  102  of spring contact surface  96  of between nine and four tenths (9.4) square millimeters and eleven (11.0) square millimeters. More preferably outer diametric measurement  98  of spring contact surface  96  is nine and one half (9.5) millimeters while inner diametric measurement  100  of spring contract surface  96  is six and one quarter (6.25) millimeters with area  102  of spring contact surface  96  of approximately ten and two tenths (10.2) square millimeters. 
     Filament  44  has an average height  106  from the closest approach of housing  24 . Additionally, filament  44  has an average spacing  108  from the closest approach of focusing portion  46 . Preferably average height  106  is between four and thirty five hundredths (4.35) millimeters and four and fifty five hundredths (4.55) millimeters while average spacing  108  is between seven tenths (0.7) millimeters and nine tenths (0.9) millimeters. More preferably average height  106  is four and forty five hundredths (4.45) millimeters while average spacing  108  is eight tenths (0.8) millimeters. 
     Prior Art Bulb Construction 
     FIG.  6  through FIG. 8 depict a pen light bulb  110 , or portions thereof, as conventionally known in the art and labeled as ‘Prior Art’. Pen light bulb  110  is comparable to the present invention. While various sizes exist for such known pen light bulbs, applicants feel that the bulb depicted, including the dimensions recited below, are representative of the state of the art. Pen light bulb  110  has a glass envelope  112 , a housing  114  and a power coupling  116 . Power coupling  116  is separated from housing  114  by an insulator  118 . Glass envelope  112  rests within housing  114  and is secured therein by material of insulator  118  which preferably extends into housing  114  to surround a terminal end, not shown, of glass envelope  112 . Glass envelope  112  is a sealed unit having electric leads as conventionally known in the art. These electric leads connects to the interior of housing  114  and to power coupling  116  respectively. 
     Glass envelope  112  has positioned therein a first power pole  120  connected to one of the electric leads and a second power pole  122  connected to the other electric lead. A spacing insulator  124  retains first power pole  120  and second power pole  122  in spaced relationship within glass envelope  112 . A filament  126  is connected to span the gap between first power pole  120  and second power pole  122 . Filament  126  produces a light when power passes therethrough. Glass envelope  112  is a continuous sealed transparent member and has a focusing portion  128 , an upper tapered portion  130 , a lower outward tapered portion  132 , a lower inward tapered portion  134  and a mounting portion, not shown, and which is contained within housing  114 . 
     Focusing portion  128  is radially disposed and has a maximum thickness  136  and a diametric width  138 . Focusing portion  128  further has a radius  140  at an exterior  142  of glass envelope  112 . Focusing portion  128  forms an optical focusing lens  144  to focus light produced by filament  126  into a beam of light  146 , see FIG. 10, having an axis of projection  148 . Maximum thickness  136  of focusing portion  128  is two and nine tenths (2.9) millimeters while diametric width  138  of focusing portion  128  is five and four tenths (5.4) millimeters while radius  140  of focusing portion  128  is two and seven tenths (2.7) millimeters. 
     Upper tapered portion  130  has a thin wall construction and is radially disposed to extend downward from focusing portion  128  a depth  150 . Upper tapered portion  130  has an angle of offset  152 , see FIG.  8 . Depth  150  of upper tapered portion  130  is three (3.0) millimeters while angle of offset  152  of upper tapered portion  130  is five (5.0) degrees. 
     Lower outward tapered portion  132  has a thin wall construction and is radially disposed to extend downward from upper tapered portion  130  a depth  154 . Lower outward tapered portion  132  has an angle of offset  156 , see FIG. 8, which is significantly greater than angle of offset  152  of upper tapered portion  130 . Depth  154  of lower outward tapered portion  132  is one and four tenths (1.4) millimeters while angle of offset  156  of lower outward tapered portion  132  is thirty nine (39.0) degrees. 
     Lower inward tapered portion  134  has a thin wall construction and is radially disposed to extend downward from lower outward tapered portion  132  a depth  158  to housing  114 . Lower inward tapered portion  134  has a radius  160 , see FIG.  8 . Depth  158  of lower inward tapered portion  134  is two and two tenths (2.2) millimeters while radius  160  is four and thirty five hundredths (4.35) millimeters. During mounting within a pen flashlight contact between pen light bulb  110  and the body of the pen flashlight typically occurs at lower inward tapered portion  134  with a portion of lower inward tapered portion  134  forming a seating surface  162 , see FIG.  8  and FIG.  12 . 
     The mounting portion, not shown, generally has a thin wall construction and is radially disposed to extend downward from lower inward tapered portion  134 . 
     Housing  114  has a circular body  164  and a circular base  166 . Housing  114  further has interior  36 , an exterior  168  and a central axis  170  extending therethrough. Exterior  168  has threads  172  positioned thereon which are not utilized for mounting when used in pen light flashlights applicable to the present invention. Circular body  164  has an upper extent  174  distal from circular base  166 . Upper extent  174  radially defines an opening, not shown, which is closed by glass envelope  112 . 
     Circular base  166  of housing  114  is generally flat with a transition  176 , which preferably is slightly rounded, between circular base  166  and circular body  164 . A spring contact surface  178  is formed by circular base  166  outside of insulator  118 . Spring contact surface  178  has an outer diametric measurement  180 , an inner diametric measurement  182  and an area  184 . In practice, when the spring is positioned between the bulb and the battery, a portion of spring  104 , see FIG.  5  and FIG. 12, often will tip off of spring contact surface  178  onto threads  172 . Outer diametric measurement  180  of spring contact surface  178  is six and fifteen hundredths (6.15) millimeters while inner diametric measurement  182  of spring contract surface  178  is five (5.0) millimeters with area  184  of spring contact surface  178  of approximately three and six tenths (3.6) square millimeters. 
     Filament  126  has an average height  186  from the closest approach of housing  114 . Additionally, filament  126  has an average spacing  188  from the closest approach of focusing portion  128 . Average height  186  is three and nine tenths (3.9) millimeters while average spacing  188  is two (2.0) millimeters. 
     Bulb Comparisons 
     Utilizing sizes and general shapes from the most preferred embodiment of self aligning pen light bulb  20  of the present invention we find various stark comparisons to the actual sizes of the example prior art pen light bulb  110 . The following relates to three primary areas of comparison. Many other differences are readily apparent. The first specific area involves the portion of the glass envelope extending out of the respective housing. The second specific area involves the housing in general and the respective circular base in specific. The third specific area involves placement of the filament relative to the respective optical focusing lens and the configuration of the respective optical focusing lens. These third specific groups of comparisons follow. 
     As can be readily observed the respective glass envelopes  22  and  112  are radically different. The improvements made to glass envelope  22  are intended to provide a more stable seating surface  78  for engagement of the body of the pen light flashlight. Seating surface  78  resides on lower tapered portion  50  which has angle of offset  76 . Depth  72  of lower tapered portion  50  is fairly long and which is two and two tenths (2.2) millimeters, with a uniform taper therealong which provides an excellent opportunity to properly seat on the portion of the pen light flashlight. This compares to seating surface  162  which resides on lower outward tapered portion  132  which has angle of offset  156 . Lower outward tapered portion  132  is fairly shallow, depth  154  which is only one and four tenths (1.4) millimeters. Incorporation of lower inward tapered portion  134  eliminates an opportunity to properly seat on the portion of the pen light flashlight. 
     As can be readily observed the respective circular bases  82  and  166  are radically different. The improvements made to housing  24  generally and circular base  82  specifically are intended to provide a more stable spring contact surface  96  for engagement of spring  104  while in the pen light flashlight. Spring contact surface  96  has area  102  which is ten and two tenths (10.2) square millimeters while spring contact surface  178  has area  184  which is only three and six tenths (3.6) square millimeters. This radical difference is accomplished despite the fact that insulator  28  consumes a greater area, inner diametric measurement  100 , which is six and one quarter (6.25) millimeters, than insulator  118  which has inner diametric measurement  182 , which is only five (5.0) millimeters. This is accomplished by expanding spring contact surface  96  out to outer diametric measurement  98 , which is nine and one half (9.5) millimeters, compared to spring contact surface  178  which only extends out to outer diametric measurement  180 , which is a mere six and fifteen hundredths (6.15) millimeters. Pen light bulb  110  relies upon the spring making contact with threads  172  which causes a tipping or twisting of pen light bulb  110  within the pen light flashlight. This action can, and often does, cause a short circuit which causes pen light bulb  110  not to function to produce light. 
     As can be readily observed the optical focusing lens  62  and  144  are radically different as is the placement of filament  44  and  126  to the respective optical focusing lens  62  and  144 . The improvements made to optical focusing lens  62  and the placement of filament  44  therebeneath are intended to provide for production of an acceptable beam of light  64 . Diametric width  56 , which is six and one tenth (6.1) millimeters, and maximum thickness  54 , which is one and eighty five hundredths (1.85) millimeters, of focusing portion  46  provide for a broader thinner lens when compared to diametric width  138 , which is five and four tenths (5.4) millimeters, and maximum thickness  136 , which is two and nine tenths (2.9) millimeters, of focusing portion  128 . This provides for a closer average spacing  108 , which is eight tenths (0.8) millimeters, of filament  44  to focusing portion  46  compared to average spacing  188 , which is two (2.0) millimeters, of filament  126  to focusing portion  128 . These improvements provide for production of a comparable beam of light  64  compared to beam of light  146 . 
     Bulb Alignment 
     FIG.  9  through FIG. 12 depict an upper portion of a pen light flashlight  190  as conventionally known in the art. The remainder of pen light flashlight  190  is not particularly relevant to the present invention. FIG.  9  and FIG. 11 depict self aligning pen light bulb  20  positioned within pen light flashlight  190 . FIG.  10  and FIG. 12 depict pen light bulb  110  positioned within pen light flashlight  190  and labeled as ‘Prior Art’. Pen light flashlight  190  has a central axis  192  extending therethrough which is the desired path of projection of a beam of light produced by pen light flashlight  190 . 
     Pen light flashlight  190 , as conventionally known in the art, has a housing  194 , a battery  196  and spring  104 . Pen light flashlight  190  has self aligning pen light bulb  20  installed therein in FIG.  9  and FIG.  11 . Pen light flashlight  190  has pen light bulb  110  installed therein in FIG.  10  and FIG.  12  and labeled as ‘Prior Art’. FIG.  9  and FIG. 11 depict the desired alignment of axis of projection  66  of beam of light  64  with central axis  192 , which is a pointing axis, of pen light flashlight  190 . This results from proper alignment of self aligning pen light bulb  20  within pen light flashlight  190 , see FIG.  11 . FIG.  10  and FIG. 12 depict the conventionally known problem wherein axis of projection  148  of beam of light  146  fails to align with central axis  192  of pen light flashlight  190 . This results from improper alignment of pen light bulb  110  within pen light flashlight  190 , see FIG.  12 . Often this misalignment problem will be even more pronounced than depicted in FIG.  10  and FIG.  12 . 
     Battery  196 , see FIG.  11  and FIG. 12, has a diameter  198  which is standardized within the industry for pen light flashlights. Spring  104 , see FIG. 5, has a diameter  200  which typically matches diameter  198  of battery  196 . Selection of diameter  200  of spring  104  within the industry for use in pen light flashlights is the result of construction of battery  196  which has a metallic housing  202  which covers the entire body of battery  196  with the exception of the central region of one end and a power post  204  centered within the central region of the one end. This provides for conductive contact with power post  204  and any part of metallic housing  202  to allow for transfer of power from battery  196 . Diameter  200  of spring  104  allows contact with a terminal end  206  of battery  196  while surrounding power post  204  without making contact with power post  204 . This provides for spring  104  to act as a conduit for the transfer of power. 
     Spring contact surface  178  of pen light bulb  110  fails to adequately support spring  104  squarely and therefore pen light bulb  110  may move out of alignment within pen light flashlight  190 , as currently commonly occurs. This improper off balanced placement of spring  104  relative to pen light bulb  110  also tends to cause spring  104  to become improperly aligned relative to battery  196 . This improper alignment of spring  104  to battery  196  may cause a short circuit where spring  104  makes contact with metallic housing  202  and power post  204 . In comparison spring contact surface  96  of self aligning pen light bulb  20  adequately supports spring  104  squarely and therefore self aligning pen light bulb  20  tends to remain aligned within pen light flashlight  190 . This proper uniform placement of spring  104  relative to self aligning pen light bulb  20  also tends to assist spring  104  to remain properly aligned relative to battery  196 . 
     Seating surface  162  of pen light bulb  110  fails to adequately support pen light bulb  110  within pen light flashlight  190 . The nature of seating surface  162  allows easy rotation of pen light bulb  110  within pen light flashlight  190  about central axis  192 . In comparison seating surface  78  of self aligning pen light bulb  20  adequately supports self aligning pen light bulb  20  within pen light flashlight  190 . Seating surface  78  actually causes self aligning pen light bulb  20  to move into proper alignment during placement into pen light flashlight  190 , or other similar flashlights. The nature of seating surface  78  resists rotation of self aligning pen light bulb  20  within pen light flashlight  190  about central axis  192 . 
     The superior seating surface, for proper placement and retention within the pen light flashlight, and the superior spring contact surface, for proper placement of the spring, combine to provide for inexpensive pen light flashlights having co-axial pointing characteristics previously found only on more expensive pen light flashlights. 
     FIG. 13 depicts a pen light flashlight  208  having self aligning pen light bulb  20  positioned therein. Pen light flashlight  208  is of a type wherein battery  196  is held in direct contact with self aligning pen light bulb  20  by spring  104 . Self aligning pen light bulbs having features of the present invention acts to provide for proper placement and retention within this type of pen light flashlight as well. 
     With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, material, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. 
     Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.