Abstract:
A modular rotatable warning light incorporates a standardized shaft, rotatable sub-assembly, motor and worm gear to form the mechanical core of the assembly. The rotatable sub-assembly includes a rotatable reflector mount supported by two axially spaced bearings for rotation around a hub. The axially spaced bearings significantly improve the function and service life of the rotatable warning light. The standardized parts are combined with a selected base plate, lamp holder, lamp and reflector to produce a modular rotatable warning light having a specified overall configuration. The efficiency of production and maintenance of various rotatable warning light configurations is improved by reducing engineering, production, maintenance and inventory costs.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to rotating warning lights intended primarily for installation on land and marine vehicles and particularly to a modular rotatable warning light sub-assembly which can be readily customized for use in conjunction with a variety of warning light systems. Additionally, this invention is directed to a modular rotatable warning light having enhanced durability and ease of manufacture, installation and maintenance. 
     2. Description of the Related Art 
     Warning light assemblies in the form of light bars mounted on emergency vehicles are well known in the art. Light bars typically employ several light sources. The light sources may be constant or pulsating. There are two basic types of light sources capable of generating a pulsating or flash pattern. These two different types of pulsed light sources consist of light sources employing gaseous discharge tubes or high-intensity incandescent lamps under electronic control and mechanically driven, i.e., rotating or oscillating light sources. The mechanically driven warning lights may employ a rotating or oscillating reflector carrying a light source. A more practical prior art arrangement moves the reflector around a stationary light source. The light source and reflector cooperate with one or more stationary lenses to produce a pulsating light pattern. Design specifications resulting from user requirements or the end-use environment dictate the particular type of pulsed light generator that is to be used in a warning light system. 
     There has been a trend toward customization and flexibility in the design and manufacture of warning light systems for use in conjunction with emergency vehicles. This trend has been driven primarily by customer demand for improvements in the visibility, durability and overall performance of warning light systems. Additionally, warning light systems are mounted to an increasing variety of vehicles for use in various air, sea and land environments. Increased customization has resulted in a proliferation of rotatable warning light subassemblies, each appropriate for a particular application. To satisfy the need for multiple versions of a rotatable warning light, engineers have increasingly employed molded plastic components for the constituent parts of these assemblies. 
     Typically, a rotatable warning light assembly includes a base configured to mount to the vehicle or light bar, a stationary lamp holder mounted to the base and a rotatable sub-assembly including a reflector mount and a reflector. The sub-assembly is arranged to rotate the reflector around a stationary lamp when driven by a direct current motor. When energized, the lamp is constantly lit and the sub-assembly is rotatably driven around the stationary lamp to produce a pulsed light pattern. 
     The rotatable sub-assembly is typically constructed of molded plastic parts consisting of a stationary hub surrounded by a rotatable reflector mount including an external gear wheel. The lamp and its associated electrical connections remain stationary within the hub. Rotational freedom between the reflector mount and stationary hub is enhanced by using a single row of spaced ball bearings that travel in races molded into the hub and lens mount, respectively. 
     Warning light systems attached to emergency vehicles are frequently exposed to the most severe environmental conditions involving physical shock, vibration and large swings in temperature, from well above 100° F. to well below 0° F. Because of exposure to large temperature differentials, tolerances within the rotatable warning light assembly must be adjusted to accommodate material expansion and contraction. The warning light assembly may also be subjected to moisture, salt, sand and windblown dust. The plastic from which the hub and reflector mount are vulnerable to wear in these harsh environments. A combination of loose tolerances and wear frequently results in poor performance and premature failure in rotatable warning light assemblies. The proliferation of rotatable warning light designs requires manufacturers and service organizations to maintain a large inventory of rotatable subassemblies to keep warning light systems for emergency vehicles operational and minimize down time. 
     There is a need in the art for a heavy duty, standardized rotatable sub-assembly having a compact and efficient configuration suitable for use in a variety of rotating warning light arrangements. 
     There is also a need for a standardized rotatable sub-assembly having significantly enhanced capability to withstand physical shock and temperature swings while having smooth and reliable rotation over a long service life. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the invention in one preferred form comprises several standardized components, including a shaft, rotatable sub-assembly, motor and drive train for use in a variety of rotatable warning light assemblies. The rotatable sub-assembly includes a reflector mount supported for rotation around a hub by two axially spaced bearings, thereby providing a more stable, durable and smoother running rotatable sub-assembly in a compact and efficient configuration. The reflector mount includes a worm wheel having gear teeth compatible with a motor driven worm gear. 
     The shaft, hub, reflector mount, motor and worm gear form the core of a modular warning light assembly. Various base plates, lamp holders, lamps and reflectors can be used in conjunction with the standardized core components to produce a variety of customized rotatable warning light assemblies. Standardized core components allow the manufacturer and service organizations to reduce inventories. 
     An object of the present invention is to provide a new and improved rotatable sub-assembly for a rotatable warning light where the sub-assembly is compatible with a wide variety of warning light configurations. 
     Another object of the present invention is to provide a new and improved rotatable warning light assembly including a heavy duty rotatable sub-assembly having improved durability and a more efficient and smooth operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings wherein like reference numerals refer to like elements in the several Figures and in which: 
     FIG. 1 is an exploded perspective view of a rotatable warning light assembly incorporating a rotatable sub-assembly in accordance with the present invention; 
     FIG. 2 is a top plan view, partially in phantom, of the rotatable sub-assembly of the rotatable warning light assembly of FIG. 1; 
     FIG. 3 is a sectional view through the rotatable sub-assembly of FIG. 2, taken along line  3 — 3  thereof; 
     FIG. 4 is a sectional view through the rotatable sub-assembly of FIG. 2, taken along line  4 — 4  thereof; 
     FIG. 5 is a partial sectional view through the shaft and base plate of the rotatable warning light assembly of FIG.  1 ;. 
     FIG. 6 is a sectional view through the shaft illustrated in FIG. 5; 
     FIG. 7 is a perspective view of the base plate of the rotatable warning light assembly of FIG. 1; 
     FIG. 8 is an exploded perspective view illustrating several alternative embodiments of rotatable warning light assembly including a standardized shaft, rotatable sub-assembly, motor and worm gear in accordance with the present invention; 
     FIG. 9 is a top plan view of the lamp holder of FIG. 1; 
     FIG. 10 is a sectional view of the lamp holder of FIG. 9, taken along line  10 — 10  thereof; 
     FIG. 11 is a top plan view of an assembled shaft, rotatable sub-assembly, lamp holder and spring clip in accordance with the present invention; and 
     FIG. 12 is a perspective view of the base plate, rotatable sub-assembly, motor, worm gear and lamp holder of FIG. 1 in an assembled configuration. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings wherein like numerals represent like parts throughout the Figures, a preferred embodiment of a modular rotatable warning light  100  is illustrated in FIG.  1 . Modular rotatable warning lights  100  in accordance with the present invention are integrated into light bar assemblies or individually mounted to vehicles to enhance the visibility and recognition of ambulances, police and fire and other emergency and service vehicles. Emergency and service vehicles are routinely exposed to extremes of heat, cold, physical shock and other wear factors such as salt and sand. 
     The core components of the modular rotatable warning light  100 , are a shaft  12 , rotatable sub-assembly  10 / 11 , motor  14  and worm gear  16 . The rotatable sub-assembly comprises a reflector mount  10  surrounding a central hub  11 . The hub  11  has an interior configuration complementary to the outside diameter of the shaft  12  so that when the rotatable sub-assembly is placed over the shaft  12 , the hub  11  is centered on and frictionally engaged with the shaft  12 . In accordance with one aspect of the present invention, the shaft  12 , rotatable sub-assembly  10 / 11 , worm gear  16  and motor  14  form a standardized mechanical heart of a rotatable warning light assembly. A variety of rotatable warning light configurations are built around these core components in a manner that will be discussed below. 
     FIGS. 2-4 illustrate the configuration of the rotatable sub-assembly  10 / 11 . The hub  11  and reflector mount  10  are symmetrically arranged around an axis of rotation A. Two axially spaced rows of bearings  17   a ,  17   b  support the reflector mount  10  for rotation relative to the hub  11 . The reflector mount  10  is preferably a molded part including an integrally molded gear wheel  9 . The gear wheel includes an arrangement of teeth configured to mesh with the worm gear  16 . The reflector mount  10  includes two axially spaced bearing races. 
     Hub  11  is also preferably a molded part including two circumferential bearing races around which the two axially spaced arrays of ball bearings  17 A,  17 B will be arranged. The two arrays of ball bearings  17   a ,  17   b  support the reflector mount  10  axially and radially relative to the hub  11 , significantly reducing the off-axis wobble present in many single-bearing designs. Two axially spaced bearings can withstand double the axial load of a single bearing of similar construction. The spaced configuration of the bearings also stabilizes the reflector mount  10  and associated reflector  40  when exposed to vibration and physical shock. 
     The hub  11  is configured with an interior diameter  13  complementary to the outside diameter  39  of the shaft  12 . In the illustrated embodiment, the outside diameter  39  of the shaft  12  is approximately  1  inch. To facilitate assembly, the interior-diameter  13  of the hub  11  is molded 0.0005″ larger than the diameter  39  of the shaft  12 . To facilitate frictional engagement between the inner surface  45  of the hub  11  and the shaft  12 , a series of ribs  19  are arranged around the interior surface  45  of the hub  12 . The ribs  19  are equiangularly spaced around the interior surface  45 . The junction of two vertical surfaces converging at a 90° angle forms each rib  19 . The axial ribs project radially inwardly from the interior surface  45  of the hub  11 , a distance of approximately 0.0005″ . The ribs are configured to deform as the hub is press fit over the shaft, providing firm frictional engagement between the hub  11  and the shaft  12 . One of skill in the art would recognize that many possible arrangements of ribs, points or protrusions of the inside surface  45  of the hub  11  or outside surface of the shaft  12  would serve this function. 
     The hub  11  and reflector mount  10  are preferably unitary molded plastic parts. Preferred materials for molding the reflector mount and hub are acetal and nylon. Warning lights in which the hub and rotatable reflector mount will be used are typically exposed to a wide range of temperatures and environmental conditions. Such large temperature differentials cause the plastic parts to expand and contract to a greater degree than would similarly configured metal parts. Tolerance considerations are critical to effectively accommodate the expansion and contraction of the plastic. If the parts are configured too tightly, then the assembly will bind when exposed to high temperatures. If the parts are configured with too loosely, cold temperatures will cause excessive play between the hub and the reflector mount resulting in a wobbly and noisy warning light assembly. Additionally, over time the plastic parts will wear, further increasing the play between the hub  11  and the rotatable reflector mount  10 . 
     A rotatable warning light in accordance with the present invention addresses the stability, wear and tolerance issues by utilizing two axially spaced rows of ball bearings  17   a ,  17   b . This arrangement provides a smooth and stable rotating assembly in which the inevitable wear is divided between the two rows of ball bearings and their associated molded races. As a result, the assembly is more stable and resistant to shock, more durable, smoother running, with a significantly longer service life. 
     FIGS. 5-7 illustrate the configuration of one preferred embodiment of the shaft  12  and its relationship to a representative base plate  30 . The shaft  12  is a hollow cylindrical part formed preferably of steel. A thin tubular extension  37  projects from one end of the shaft. This thin tubular extension  37  is deformed or swaged around an opening  31  in the base plate  30  to form a secure engagement  37   a  between the shaft  12  and the base  30 . The axially opposed end of the shaft defines a symmetrical arrangement of four equiangularly spaced rectangular slots  35 . An outward facing circumferential groove  36  traverses the exterior of the shaft  12  at approximately the axial midpoint of the rectangular slots  35 . 
     FIG. 7 illustrates a representative base plate  30  to which the components of the rotatable warning light assembly  100  can be mounted. Although the configuration of the base plate  30  will vary depending upon the ultimate configuration of the warning light system, all the base plates will have several elements in common in accordance with one aspect of the present invention. First, each base will include an opening  31  configured to receive the tubular extension  37  of the shaft  12  as is best illustrated in FIG.  5 . Each base plate also includes a motor bracket such as  38 . The base plates also include a structure for mounting the base plate to the vehicle or warning light system. 
     While the configuration of the base plate  30  can change as needed to meet specifications, the shaft  12  and motor  14  configuration are intended to remain the same. As a result, the general configuration of the opening  31  and motor mount  38  on any particular base plate  30  will be substantially similar in accordance with the present invention. Preferred materials for the base plate and shaft are steel. A steel substructure provides additional support, stability and rigidity to the rotatable warning light assembly  100 . Moreover, the shaft  12  and base plate  30  are intended to be permanent parts while wear items such as the motor  14 , worm gear  16 , reflector mount  10  and hub  11  are configured as easily replaceable, standardized items. 
     The slotted configuration of the shaft  12  is arranged to be compatible with the base portion of a lamp holder  20 . FIGS. 1,  9 , and  10  illustrate a representative configuration for a lamp holder  20 . The lamp holder  20  is essentially a cylindrical molded plastic part having a plurality of radially projecting legs  21  extending from a base portion and including an axially opposed lamp-receiving socket. With reference to FIG. 9, the socket includes receptacles  23  that provide locations for the retention of electrical connectors (not illustrated). The socket provides an interface between the lamp and the electrical conductors  24 . Each lamp holder  20  will project above the base portion and legs  21  a distance dictated by the desired configuration of the rotatable warning light assembly. The socket in each lamp holder  20  is of course configured to retainably receive the lamp dictated by the overall design. It should be emphasized that while the base portion and legs  21  will be standardized for interaction with the slotted shaft  12 , the configuration of the remainder of the lamp holder can be selected to meet the specifications of a desired rotatable warning light assembly. The socket may include a slot  25  or other arrangement to index the bulb with respect to the lamp holder as is known in the art. 
     FIG. 1 is an exploded view of a representative rotatable warning light assembly  100 , including the standardized shaft  12 , reflector mount  10 , hub  11 , motor  14 , and worm gear  16 . With reference to FIGS. 3 and 4, the lower end  35  of the hub  11  is configured to protrude below the rotatable reflector mount  10 . During assembly, the rotatable sub-assembly  10 / 11  is forced over the shaft  12  until the lower end  35  of the hub  11  contacts the top surface of the base plate  30 . The axial installation force is exerted on the top surface  33  of the hub  11  so that excessive pressure is not placed on the bearing assemblies  17   a ,  17   b  connecting the hub  11  with the reflector mount  10 . A selected lamp holder such as lamp holder  20  is arranged so that the legs  21  align with the slots  35  of the shaft  12 . The lamp holder  20  is then axially inserted into the shaft  12 . 
     The installed relationship between the lamp holder  20 , hub  11  and shaft  12  is best illustrated in FIGS. 11 and 12. From the overhead view of FIG. 11 it can be seen that each leg  21  is configured to protrude radially beyond the shaft and project over the upper surface  33  of the hub  11 . A snap ring  22  is inserted in circumferential groove  36  of the shaft  12 , thereby retaining both the lamp holder  20  and the hub  11  in fixed relationship to the shaft  12 . The rotatable sub-assembly  10 / 11  is thus securely mounted around the shaft  12  and adjacent the base  30 . 
     With reference to FIG. 1, electrical leads  24  are threaded through the axial opening in the shaft  12  and into the lamp holder receptacles  23  where they form a junction for providing power to the lamp  42 . During operation of the rotatable warning light assembly  100 , the shaft  12 , hub  11 , lamp holder  20  and lamp  42  remain stationary while the reflector mount  10  and reflector  40  rotate about the lamp. The reflector mount  10  includes a series of bores  15  for the reception of mounting hardware (see FIGS. 2,  3 ). FIG. 1 illustrates a representative reflector  40  configured to pass over the lamp holder and lamp to interface with the reflector mount  10 . 
     It should be recognized that the lamp holder  20 , lamp  42  and reflector  40  together define an optical system that will provide a pre-established light pattern according to a given specification. The lamp holder, lamp and reflector selected also determine the axial height and radial dimensions required for operation of the rotatable warning light assembly  100 . Alternative lamp holders, lamps and reflectors will of course be selected to meet the spatial constraints dictated by the overall rotatable warning light assembly system configuration. 
     FIG. 8 is an exploded view illustrating the standardized shaft  12 , reflector mount  10 , hub  11 , motor  14 , and worm gear  16  in functional conjunction with a variety of base plates  30 ,  30   a ,  30   b ,  30   c ,  30   d , lamp holders  20 ,  20   a ,  20   b , and reflectors  40 ,  40   a ,  40   b . It can be seen from this illustration that the standardized shaft  12  can be mounted to a variety of base plates  30 ,  30   a - 30   d . It should be noted that each of the base plates includes an aperture for swage mounting of the shaft  12 , as well as a motor mount bracket and a structure for securing the base to a vehicle or warning light assembly. Each of the lamp holders  20 ,  20   a ,  20   b  includes a substantially similar arrangement of radially projecting legs configured to mate with the slotted end of the shaft  12 . Each of the reflectors  40 ,  40   a ,  40   b , while having alternative height, width and optical configurations, includes slots or holes configured to align with the bores provided in the reflector mount  10 . The use of standardized parts simplifies the creation of a variety of rotatable warning light assemblies. Further, maintenance of the several assemblies is simplified because the wear items are standard interchangeable parts easily removed and replaced. 
     While a preferred embodiment of the foregoing invention has been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations, and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.