Abstract:
An improved marker light for temporary or emergency use in delineating the boundaries of safe aircraft landing areas and for other signalling purposes, the marker light having a cylindrical housing secured to the exterior of a ballast bag and provided with a lamp assembly and cover, the marker light being activated by rotation of the cover.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a marker light for temporary or emergency use in delineating the boundaries of safe aircraft landing areas, for marking roadways or obstructions or for other signaling purposes, generally of a temporary nature. More particularly, it relates to a self-contained, battery powered light, combined with an optional ballasted supporting base, which may be rapidly deployed on or near selected sites, as by tossing the light assembly from a moving vehicle. 
     BACKGROUND OF THE INVENTION 
     Marker lights of the type herein involved are used primarily by military forces in combat areas to mark the boundaries of safe aircraft landing areas or drop zones, to mark roadways or obstructions and for a variety of other signalling purposes where it is desirable to provide some visible indication of either safe or hazardous conditions, without requiring manned attendance. Such uses are usually of a temporary or emergency nature and conditions often require that the markers be easily transported then rapidly deployed with a minimum amount of attention to their secure and precise placement. Often, the marker lights are distributed by dropping the lights at intervals from a moving vehicle. Such a method requires that the marker lights be capable of erecting themselves to an operative position at or near their intended location and that they remain reasonably well fixed on site. 
     Marker lights designed specifically for such purposes are disclosed in U.S. Pat. No. 2,806,131, issued Sep. 10, 1957 and U.S. Pat. No. 4,563,668, issued Jan. 7, 1986 and in U.S. Military Specification MIL-L-52543C, dated Oct. 7, 1976, available from Commander, US Army Mobility Equipment Research and Development Command, ATTN: DRXFB-DS, Fort Belvoir, Va. 22060. 
     The marker lights disclosed in the above references comprise a cylindrical housing closed at the bottom end. The lower portion of the housing encloses a dry cell battery above which is mounted a three position switch and a printed circuit board supporting a lamp flasher circuit. The switch operating lever extends to the exterior of the housing and is covered by a rubber boot. The printed circuit board is covered by a dome-like light deflector extending completely across the housing and having a white or reflective finish with a lamp socket and lamp mounted centrally thereon. The lamp and light deflector dome are covered by a transparent protective dome which has an outwardly projecting flange at the open end in abutment with the upper edge of the cylindrical housing. The protective dome and the underlying deflector dome are secured in position closing the upper end of the cylindrical housing by an internally threaded ring that engages mating threads formed around the outer upper edge of the cylindrical housing. The ring has an inwardly directed flange at its upper edge which captures the flange of the protective dome, along with a sealing gasket, and draws the dome and light deflector into a tightly seated contact with the upper rim of the housing. 
     The lower, major portion of the light housing is inserted through the neck of a ballast bag, extending into the interior of the bag. Prior to assembly of &amp;.he light housing to the ballast bag, the bag is substantially filled with any suitable and available ballast material, such as sand, stones, soil or ice. The bag is then closed by inserting the light housing through the bag neck and tightly clamping the edge of the bag neck against the light housing by means of a hose clamp or similar device. In certain marker lights of the prior art, the ballast bag includes, in addition to the opening through which the light assembly is inserted, one or more openings fitted with flap closures to permit filling the bag with ballast without disturbing the assemblage of the light housing to the ballast bag. 
     Prior marker lights of the type described are prone to certain failures and disadvantages. The primary cause of failure is damage to the light assembly housing and various parts of the light assembly resulting from impact cf the marker light with the ground when the light is dropped from a moving vehicle. Disadvantages of the prior marker lights include: difficulty in installing the light assembly into the filled ballast bag; impact damage to the light housing when the ballast comprises hard, sharp material, such as rocks; difficulty in filling the bag completely with ballast material because of the inaccessibility of areas of the bag in the vicinity of the light housing; loss in stability because of the reduced capacity of the bag for ballast material, due to the presence of the light housing; poor low temperature performance when the light housing is frozen into cold ballast material, such as ice; difficulty in adjusting the light dome for directional control when a partially blacked-out light dome is used and difficulty in changing the light color when lights of various colors are used. Other shortcomings of prior marker lights will become evident hereinafter. 
     It is an object of the invention to provide a marker light of the type described having improved immunity to damage resulting from the shock of deployment. 
     Another object of this invention is to reduce the maintenance time on the marker light. The switch contact is frequently subject to premature failure due to environmental factors such as hot humid climates and other factors such as the destructive vapors emitted by deteriorating batteries. Therefore, improved and rapid maintenance is achieved when the switch contact is a component of the cover or circuit so that it is quickly replaced as the appropriate one of these components is replaced. 
     Another object of this invention is to provide a more compact marker light. 
     It is a further object of this invention to provide a marker light that functions with less components. 
     It is another object of this invention to provide a marker light that can have its circuit and switch contact simultaneously replaced during maintenance of one of these components without the prior necessity of disconnecting the switch from the housing. 
     It is another object of the invention to provide a marker light having a ballasted supporting base in which the light assembly is isolated from direct contact with the ballast material thereby reducing the likelihood of damage to the light assembly by impact of the ballast material against the light assembly and reducing the possibility of deterioration of the light assembly by moisture seepage from the ballast material into the light assembly, should the light assembly housing be fractured during deployment, and improving cold weather performance by eliminating the possibility of the battery case being frozen into the ballast. 
     It is another object of the invention to provide a marker light having an optional supporting base in the form a bag having a reclosable opening to permit filling the bag with available ballast material in which the interior of the bag is not obstructed by the housing of the marker light thereby increasing the capacity of the bag for ballast material, improving the stability of the marker light and permitting the bag to be filled completely through a single opening. 
     It is another object of the invention to provide a ballasted marker light which is rainproof without the use of rubber seals, and in which the light circuit connections and switch are formed by a printed circuit board, eliminating jumper wires and a discrete switch and in which the light circuit is opened when the cover is removed from the battery housing, thus precluding accidental or inadvertent illumination of the lamp when the lamp housing is partially disassembled. 
     It is a further object of the invention to provide a marker light in which the lamp bulb can be easily replaced, the color of the light can be easily changed and the directivity of the light can be easily altered. 
     It is still another object of the invention to provide a marker light of simplified construction and reduced cost of manufacture. 
     Other objects and advantages of the invention will become apparent as an understanding thereof is gained from the following complete description and the accompanying drawings. Brief Description of the Invention 
     Briefly, the marker light of the present invention comprises a marker light assembly having a cylindrical base portion closed at the bottom end and open at the top end which contains a battery compartment and storage space for spare lamp bulbs and bulb covers. The top end of the base portion is provided with three upwardly extending clamp arms spaced evenly about and spaced outward from the top rim of the base. A segmented flange extends outward from the top rim of the base near the lower ends of the clamp arms. The top end of the base is closed by a convex cover having a downwardly extending cylindrical rim with an outwardly projecting flange at the lower edge. The rim of the cover overlaps the top upper edge of the base. 
     A printed circuit board is mounted on the under side of the cover. The board includes a downwardly facing circuit pattern having contacts for engaging the battery terminals to connect the batteries either directly to the lamp for continuous illumination of the marker light or to an interrupter circuit through which the lamp receives intermittent power for flashing illumination of the marker light or for open circuiting the lamp. Thus, rotation of the cover with respect to the base orients the circuit board in three different azimuthal positions to perform the function of a three position switch having &#34;on&#34;, &#34;off&#34; and &#34;flash&#34; positions. The cover is indexed to the base for proper orientation of the circuit board by an actuating arm which projects downward from the outer rim of the cover through a slotted flange extending outward from the upper end of the base. 
     A lamp socket, mounted on the upper surface of the board, projects through the center of the cover to receive a lamp. Components of the interrupter circuit are also mounted on the upper surface of the board. The lamp is optionally covered by a small translucent inner dome which may be colored with any of the conventional signal colors, such as red, green or amber. 
     The cover and inner dome are enclosed by a large, transparent outer dome which may be partially covered by an opaque finish so that the light will be visible only from a particular direction of approach. The lower rim of the outer dome is dimensioned to fit snugly over the cylindrical rim of the cover and is provided with an outwardly projecting flange which overlies and abuts against the flange of the cover. The outer dome is installed over the cover and the outer dome and cover are pressed down over the upper rim of the base until the flange of the outer dome is gripped by the clamp arms of the base. A secure assemblage of the cover and outer dome to the base is thus formed in which both the cover and the outer dome are relatively easily rotatable with respect to the base. The edge of the outer dome overlapping the upper rim of the base forms a rainproof seal without the use of a rubber gasket or a switch protective boot. 
     The marker light assembly can be used alone but is usually secured to the upper outer surface of a ballast bag, preferably by a pair of spaced rivets or removable nuts and screws passed through the bottom of the base of the light assembly and through the upper surface of the ballast bag. The bag may be suitably formed like a pillow case with an opening along one edge for inserting the ballast material, which may be closed by a zipper or snap fasteners or other suitable means. Tie down loops may also be attached to the corners of the bag for fixing the marker light in place by means of stakes or other suitable anchoring devices. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevation of a typical marker lamp of the prior art, with a portion of the ballast bag thereof broken away to show the seating of the light housing within the ballast; 
     FIG. 2 is an elevation of a marker light constructed in accordance with a first embodiment of the invention, with a portion of the ballast bag thereof broken away to show the separation of the ballast from the light housing; 
     FIG. 2A is a sectional view, taken along the line 2A--2A of FIG. 3, of one of the clamp arms used to secure the cover and light dome to the light housing; 
     FIG. 3 is a top view of the marker light of the first embodiment of the invention; 
     FIG. 4 is an exploded elevation of the first embodiment of the invention with the facing wall of the housing thereof broken away; 
     FIG. 5 is a top view of the housing of the marker light of the invention with the cover and light dome removed; 
     FIG. 6 is a bottom view of the cover for the housing of the first embodiment of the invention; 
     FIG. 7 is a vertical section of an assembled marker light constructed in accordance with a second embodiment of the invention; 
     FIG. 8 is a top view of the second embodiment of the invention; 
     FIGS. 8A-8C are fragmentary sections of the upper portion the second embodiment of the invention taken along the lines 8A--8A, 8B--8B, and 8C--8C of FIG. 8, respectively; 
     FIG. 9 is an elevation of the cover of the marker light of the second embodiment of the invention; and 
     FIG. 10 is a bottom view of the cover shown in FIG. 9. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is an elevation of a typical marker light of the prior art. The marker light comprises a cylindrical housing 10 containing a battery, usually a 6 v. lantern battery, in the lower portion and a circuit board, for mounting the components of an interrupter circuit and spare bulb carriers, in the upper portion. A three-position toggle or slide switch is mounted in the upper portion of the housing with the operating lever 11 thereof projecting outward to enable the selection of &#34;off&#34;, &#34;on&#34; or &#34;flash&#34; operation of the light. The housing is closed at the upper end by a convex light deflector 12, having a lamp socket and lamp 13 mounted in the center thereof, and by a transparent dome 14 which surrounds and extends over the light deflector and lamp. The light deflector 12 and dome 14 are secured to the housing by an internally threaded, flanged ring 15 and a sealing gasket (not seen) that abuts against a flange on the rim of the dome. The deflector 12, dome 14 and gasket are drawn tightly against the upper edge of housing 10 as the ring 15 is threaded down onto mating threads at the upper end of housing 10. 
     The lower portion of the housing 10 is fitted into the neck of a ballast bag 16, which is filled with any available ballasting material, where it directly contacts and becomes immersed in the ballast. The bag may be provided with an auxiliary opening with closure means for filling the bag with ballast, other than through the neck of the bag. The bag 16 is secured to the housing 10 by a hose clamp 18, or an equivalent, which tightly seals the neck of the bag to the housing. 
     Marker lights as shown in FIG. 1 are susceptible to damage from impact with the ground, which can occur when the lights are deployed by dropping them from a vehicle. The light is fairly tightly constrained, both against rotational and translational motion with respect to the ballast bag, and the light housing is in direct contact with the ballast. When the bag is impacted, forces are transmitted through the ballast to the light assembly, which can absorb only a small amount of the impact energy through inertial motion, and the light assembly may become overstressed at one or more points, resulting in breakage. Should a crack occur in the lower portion of the housing, the direct contact of the housing with the ballast permits moisture to seep from the ballast into the housing. The light dome 14 is tightly constrained about its rim by the ring 15, severely limiting &amp;:he freedom of the dome to flex to relieve stress. If the dome is struck by a direct blow or is otherwise overstressed, the possibility of its fracture is thereby increased. 
     The light dome 14 is tightly secured to the housing 10 by the ring 15 and sealing gasket. If the light dome is partially blacked-out to control the directivity of the light and it is desired to change the direction from which the light is visible, it is necessary to loosen the ring to permit rotation of the dome relative to the housing and thereafter retighten the ring. Such an operation is time consuming and may expose personnel to hazards under combat conditions. The switch protective boot and the switch location both obscure the position of the switch lever so that, during battery replacement or o&amp;her maintenance, the light may be reassembled with the switch in an operating position, which could lead to early battery failure or the inadvertent activation of the light under blackout conditions. Filling the ballast bag with chunky ballast, such as rocks, is difficult and unreliable because the battery housing obstructs the void at the back of the bag. Two openings may be provided in the bag on opposite sides of the housing, but this increases the time and effort of filling the bag, as well as the cost of manufacture. 
     No convenient means are provided for changing the color of the light. If the light color is to be changed, a light dome of the selected color must be substituted for the light dome then in use. No provision is made for insuring that light domes of various colors will be at hand continuously, as these must be carried separately from the marker light, thereby multiplying storage and supply problems. 
     The foregoing disadvantages and limitations of marker lights of the prior art are overcome by the marker light of the present invention, two embodiments of which will next be described with reference to FIGS. 2-10. 
     Referring to FIGS. 2, 3 and 4, the first embodiment of the marker light of the invention comprises a cylindrical housing 21 having three clamp arms 22, 22&#39; and 22&#34; evenly spaced about the upper end thereof. As best seen in FIG. 4, the housing 21 is closed at its upper end by a cover 23 formed with a convex upper surface 24 and a cylindrical rim 25 having an inner diameter dimensioned for a close rotational fit over the upper edge of housing 21. Rim 25 extends downward below the upper edge of housing 21 when assembled thereto. A circular flange 26 extends outward from the periphery of the lower edge of rim 25. An actuating arm 27, the purpose of which will later be described, projects from flange 26 and extends downward below the lower surface of the rim. A lamp socket 28 and lamp 29 project upward from the center of cover 23. The lamp 29 is covered by a transparent inner light dome 31 which may be either clear or colored with any of the conventional signal colors, such as red, green or amber. Cover 23 is finished with a white or similar light reflective surface. 
     A generally circular, transparent outer light dome 30 is superimposed over cover 23. The inner wall of the lower end of light dome 30 is cylindrical with a diameter dimensioned for a close rotational fit over the rim 25 of cover 23. An outwardly extending flange 32 encircles the lower periphery of dome 30. One or more portions of light dome 30 may be blacked-out with an opaque finish, as seen at 33, FIG. 4, so that the light may be seen only from a particular direction of approach. 
     Referring to FIGS. 2, 2A and 3, the clamp arms 22, 22&#39; and 22&#34; are formed with a horizontal arm 35 projecting outward from below the top edge of housing 21 and a vertical arm 36 extending upward to the level of the top edge of housing 21. A downwardly inclined ramp 37 projects inward from the inner surface of arm 36. A segmented flange 38 substantially encircles housing 21 at a level slightly above the level of the upper surface of arm 35 to serve as a stop when the cover 23 and the light dome 30 are fitted over housing 21 and to serve as a bearing surface when the cover or light dome is rotated relative to the housing. The distance separating the upper surfaces of flange 38 and the ledge at the end of ramp 37 is slightly greater than the combined thicknesses of flanges 26 and 32. 
     As best seen in FIG. 2A, the outer diameters and the widths of flanges 26 and 32 of the cover 23 and light dome 30 are such as to provide clearance between the edges of the flanges and the inner surface of arm 36. When the cover 23 and light dome 30 are fitted over the housing 21 and pressed down into place against flange 38, the clamp arms 36 are flexed outward by passage of the edges of flanges 26 and 32 over the ramps 37 until flange 32 passes over the ends of the ramps. At that point, arms 36 return to their original position and the cover and light dome are held in place by the upward thrust of the batteries within the housing 21 against the cover 23, as will later be more fully described. It is to be noted that the extension of the lower edge of light dome 30 below the upper edge of housing 21 effectively seals the housing against the entry of moisture from rain or other sources. 
     Referring to FIGS. 3 and 4, the inner light dome 31 is formed with three tabular flanges 41 equally spaced about the lower edge thereof. Dome 31 is seated over the lamp 29 and the dome is rotated to carry the tabs 41 through slots 42, formed on the inner sides of posts 43 upstanding from the surface of cover 23, and against the stops 44 (FIG. 3). 
     Referring to FIGS. 4 and 5, the housing 21 is partitioned to form an off center battery compartment 45 sized to contain four C-type alkaline dry cells 46-49. The vertical line passing through the center of gravity of said bottom of said housing is laterally spaced at least 1/4 inch away from the vertical line passing through the center of gravity of said battery. Two leaf spring contacts 51, 52 are secured to the bottom of compartment 45 to connect, respectively, the negative terminal of cell 46 with the positive terminal of cell 49 and the positive terminal of cell 47 with the negative terminal of cell 48. In the space adjacent to compartment 45, the bottom of housing 21 is fitted with a holder (not seen) upon which are stacked inner light domes 31&#39; of various colors, available for use at any time, and with holders (not seen) for spare lamp bulbs 29&#39;. 
     FIG. 6 is a bottom view of the cover 23 showing the printed circuit board 54 mounted on the underside thereof. The board 54 rests on four mounting posts 55, extending downward from the under surface of cover 23, and is secured to the cover by a mounting screw 56. The circuit pattern cf board 54 includes a stud contact 57 connected by a conductive path 58 to the negative terminal of lamp holder 28; a stud contact 60 connected by a conductive path 61 to a contact pad 62; a contact pad 63 connected by a conductive path 64 and wire 65 to the positive terminal of lamp holder 28 and a contact pad 66 connected to components of an interrupter circuit (not seen) mounted on the upper surface of board 54. Interrupter circuits suitable for use herein are well known in the art. The end of the interrupter circuit opposite contact pad 66 is connected to the positive terminal of lamp holder 28. 
     When the cover 23 is fitted over the end of housing 21, spring contacts 51 and 52 thrust cells 46-49 upward so that stud contact 60 bears against the negative terminal of cell 49, contact pad 62 bears against the positive contact of cell 48, stud contact 57 bears against the negative terminal of cell 47 and the positive contact of cell 46 bears either against contact pad 63, contact pad 66 or a point between contact pads 63 and 66, depending upon the azimuthal angle of cover 23 with respect to housing 21. Cover 23 is indexed in azimuth with respect to housing 21 by actuating arm 27 which extends downward through the slot 68 of an index flange 70 (FIG. 5) projecting outward from near the upper end of housing 21. The cover 23 may be rotated with respect to the housing 21 through a limited arc, defined by the length of slot 68. During such travel, as actuating arm 27 is moved from the left end of slot 68 to the right end thereof, actuating arm 27 passes through three switch positions comprising &#34;flash&#34;, &#34;off&#34; and &#34;on&#34;. Indicia of these positions may be marked on the upper surface of flange 70. 
     With actuating arm 27 located at the left end of slot 68 in the &#34;flash&#34; position, the positive terminal 72 of cell 46 contacts contact pad 66; contact pad 62 contacts the positive terminal 73 of cell 48; contact 57 engages the upwardly facing surface of cell 47, comprising the cell negative terminal and contact 60 engages the upwardly facing surface of cell 49, also comprising the cell negative terminal. Cell 46 is connected in series with cell 49 by contact spring 51 and cell 47 is connected in series with cell 48 by contact spring 52. Thus all four cells are connected in series with the interrupter circuit and the lamp 29 for flashing operation of the lamp. The series circuit can be traced as follows: commencing with contact 57, the negative terminal of cell 47 and the negative terminal of lamp holder as the most negative point of potential, the circuit proceeds through the positive terminal of cell 47 and contact 52 into the negative terminal of cell 48; then from the positive terminal 73 of cell 48 through contact pad 62 and contact 60 into the negative terminal of cell 49; then from the positive terminal of cell 49 through contact 51 into the negative terminal of cell 46; then from the positive terminal 72 of cell 46 in contact pad 66 and through the interrupter circuit to the positive terminal of lamp 29. 
     When the cover 23 is rotated relative to the housing 21 through the arc defined by slot 68, contacts 57 and 60 travel across the negative terminals of cells 47 and 49 along the paths indicated by arrows 75 and 76, respectively, and contact pad 62 travels across the positive terminal 73 of cell 48 along the path indicated by arrow 77. Contact pads 66 and 63 travel across the positive terminal 72 of cell 46 along the path indicated by arrow 78. Throughout such travel, contacts 57 and 60 and contact pad 62 are in continuous contact with their associated negative and positive terminals of cells 47, 49 and 48. Contact pads 66 and 63 occupy three successive positions in moving from left to right, in which: the positive terminal 72 of cell 46 contacts pad 66 for &#34;flash&#34; operation of the lamp; positive terminal 72 lies intermediately between pads 66 and 63, turning the lamp off, and positive terminal 72 contacts pad 63 for continuously &#34;on&#34; operation of the lamp. 
     Referring to FIGS. 2 and 4, the marker light assembly is secured to the top surface of a ballast bag 80 by two aligned rivets 81 passed though the bottom of housing 21 along the center line thereof and through the upper layer of bag 80. Bag 80 is open along one edge thereof, forming a flap 82, to enable the filling of the bag with whatever ballast material 83 that may be available and suitable for the purpose. Any suitable fastening means, such as snap fasteners 84, as shown, a zipper or other means, may be used to secure flap 82 closed to prevent spillage of the ballast. The bag may be provided with tie-down loops 86 fixed to the corners of the bottom surface of the bag for anchoring the marker light in place. 
     FIGS. 7-10 illustrate a second embodiment of the invention which differs primarily from the embodiment described with reference to FIGS. 2-6 in the pivotal mounting of the circuit board 54 to the cover 23A, which is modified from the cover 23. The housing 21, the interior arrangement of housing 21, the outer light dome 30 and the inner light dome 31 are the same for both embodiments of the invention. 
     Referring to FIGS. 7 and 10, circuit board 54 is pivotally attached to the cover 23A by a mounting screw 90 passed through circuit board 54 near the edge thereof adjacent to the lamp holder 28. Screw 90 is seated in a mounting post 91 that depends from the inner surface of cover 23A and serves as a bearing point for board 54. An alternate actuating arm 92 is attached to board 54 near the edge thereof opposite screw 90, as by rivets 93 or other suitable fasteners. Alternate activating arm 92 extends outward over the top edge of housing 21 and downward along the outer surface of housing 21 parallel to the inner vertical wall of said dome through slot 68 of flange 70. In this embodiment, the actuating arm 92 is a discrete component with a vertical element wherein in the FIG. 4 embodiment, the vertical element of the actuating arm 27 is an integral part of rim 25 of the cover 23. Alternate activating arm 92 may be manipulated in the same manner as actuating arm 27 to establish the circuit connections of &#34;on&#34;, &#34;off&#34; and &#34;flash &#34; to the lamp 29. In the first embodiment, the circuit board 54 and cover 23 rotated together to change circuit connections. In the second embodiment, cover 23A remains stationary while the board pivots relative to the cover to change circuit connections. The motion of circuit board 54 with respect to the batteries 46-49 is the same in both embodiments of the invention. 
     Cover 23A of the second embodiment is modified from cover 23 of the first embodiment to permit lever 92 to clear the cover 23A and extend to the exterior of housing 21. Referring particularly to FIGS. 9 and 10, cover 23A terminates in a circular outer edge 94 having a diameter substantially equal to the inner diameter of outer dome 30 at the lower end thereof. Two diametrically opposed legs 95, 96 extend vertically downward from the edge 94 of cover 23A. Flanges 95&#39;, 96&#39; respectively extend horizontally outward from the lower ends of legs 95, 96. As seen in FIG. 8C, when the cover 23A and outer dome 30 are assembled to the housing 21, flange 32 abuts against flange 96&#39;, and similarly flange 95&#39;, to secure cover 23A against upward motion relative to the housing 21, while the vertical portions of legs 95, 96 are sandwiched between the inner surface of the lower end of dome 30 and the upper, outer surface of housing 21 to maintain the cover 23A in proper horizontal alignment with the housing 21. As seen in FIGS. 8A-8C, legs 95, 96 are of proper length to maintain a clearance space 97 between the edge 94 of cover 23A and substantially the entire periphery of the upper end of housing 21. The extension of lever 92 from the circuit board 54 through the clearance space 97 to the exterior of the housing 21 can be seen in FIG. 7. 
     The marker light of the invention has numerous advantages over marker lights of the prior art. The mounting of the marker light assembly to the ballast bag in the manner described has the advantage that the light assembly may rotate or translate, both horizontally and vertically, a limited amount, as permitted by the slack in the fabric of the ballast bag, to absorb through inertial motion the impact forces generated in dropping the marker light from a height. The off-center mounting of the batteries within the housing of the light assembly tends to promote such absorption of impact forces by the inertial rotation light assembly. The isolation of the light assembly from direct contact with the ballast material contained in the bag allows impact forces to be largely absorbed by displacement of the ballast material within the bag prior to the imparting of such forces to the light assembly and further prevents the seepage of moisture from the ballast material into the housing of the light assembly, should the housing become cracked during deployment of the marker lights. In situations where the ballast material used is snow or ice, the isolation of the housing from the ballast prevents the ballast from chilling the battery contained in the housing and degrading the performance of the marker light. 
     The construction of the printed circuit with switch terminals formed as an integral part and the mounting of the printed circuit board for relative motion with respect to the battery eliminates the costly switch used in prior marker lights. In the invention, the switch position is not obscured by a protective boot, as in prior marker lights. The marker light of the invention may be disassembled for battery replacement or other maintenance and then reassembled with assurance as to the switch position, thus precluding the possibility of inadvertently assembling the marker light with the switch in an operating position. The extension of the lower edge of the outer light dome below the upper edge of the housing effectively seals the housing against the entry of moisture while still permitting easy rotation of the cover and light dome relative to the housing. 
     The provision of the inner light dome and storage space for light domes of various colors enables the color of the marker light to be easily changed. The manner of mounting the cover and outer light dome to the housing of the light assembly improves the immunity of the light assembly to damage from direct blows and permits the ready adjustment of the light dome to control the directivity of the marker light. 
     Obviously, modifications and variations in the construction of the marker light of the invention are possible in the light of the above teachings. The invention may be practiced otherwise than as specifically disclosed without departing from the spirit and scope of the appended claims.