Sports lighting luminaire having a broken glass safety shutdown circuit

A sports lighting fixture having a broken glass detection arrangement includes a high intensity light source disposed near the closed end of a reflector member. A cover member made of a light transmissive material is disposed at the open end of the reflector and is effective for filtering UV radiation emitted by the light source. A ballast circuit has in input portion receptive of line power and an output portion effective for conditioning the line power to energize the light source. A conductor strip is disposed on the cover member and is effective such that, when the cover member is intact, an electrical signal can be passed therethrough. An interruption circuit arrangement is electrically coupled into the ballast circuit and has the conductive strip disposed therein so that, upon the occurrence of an open condition in the conductive strip, indicative of a broken glass condition, the interruption circuit arrangement is effective for interrupting current flow in the ballast circuit thereby resulting in a shutdown of power to the light source and the consequent prevention of further UV emission until such time as the cover member is replaced.

FIELD OF THE INVENTION 
This invention relates to a sports lighting luminaire having a broken glass 
safety shutdown circuit. More particularly, this invention relates to such 
a sports lighting luminaire which exhibits improved photometric 
performance using an arc tube in a parabolic reflector, the luminaire 
having a tempered glass cover to provide filtering of ultraviolet 
radiation (UV) and wherein a safe and cost efficient circuit is provided 
to insure that upon breakage of the cover, the light source is shut down 
so as to substantially prevent the emission of UV. 
BACKGROUND OF THE INVENTION 
Architectural lighting designers, faced with the task of uniformly and 
efficiently illuminating the playing surface of a sports field while 
minimizing the amount of light spilled into the seating portion of the 
sports field, have utilized individual lighting fixtures that would be of 
a type that utilized a large light source having an arc tube disposed 
within an outer envelope that was oriented along the central axis of the 
light source. The light output pattern of such a fixture would be of a 
circular shape such that, once directed onto the playing surface of a 
sports field, resulted in an essentially elliptically shaped light pattern 
with varying amounts of light intensity around such elliptical shape. This 
approach suffers in terms of light utilization and the amount of spill 
light experienced; that is, the amount of light that goes beyond the 
playing surface and into the eyes of the spectators and in worst cases, 
beyond the confines of the sports field to surrounding homes and 
businesses. Because this fixture utilized a light source along the central 
axis of the reflector with little regard for the amount of light exiting 
the fixtures at high angles thereby resulting in such spill light, the 
size constraint of an outer jacket to the light source was not of critical 
consideration and such outer jacket could be utilized for the purpose of 
UV filtering from the arc tube disposed within the outer jacket. Although 
this approach has proven effective in providing a means of filtering UV 
radiation emitted by the high intensity light source, the consequences of 
such an approach in terms of light utilization and spill light has had 
adverse effects. For instance, since the elliptical light pattern results 
in an inefficient combination of patterns at the playing field surface, 
there is the need to increase the actual number of fixtures needed to 
illuminate a particular area and the need to provide external light 
directing devices such as glare shields and louvers. U.S. Pat. No. 
4,725,934 issued to Gordon et al on Feb. 16, 1988, discloses a fixture 
using an outer jacketed light source disposed along the longitudinal axis 
of a reflector as well as external louvers and a glare shield for 
redirecting light otherwise falling at higher output angles than desired. 
A sports lighting luminaire presently offered by GE Lighting Systems 
Department of General Electric Company under the product name "UltraSport" 
provides a solution to the problem of efficiency of light output and the 
reduction of spill light or glare. In attempting to improve the light 
delivery characteristics of sports lighting luminaires, the assignee of 
the present invention has developed the new sports lighting luminaire 
wherein a high intensity light source is utilized within a parabolically 
shaped reflector. In order to prevent the emission of UV radiation from 
such light source, the sports lighting luminaire uses a tempered glass 
cover for filtering UV. 
One problem with the use of a separate cover member to serve the purpose of 
UV filtering is that, should the cover be broken for instance by vandalism 
or by accident relating to the sporting event at the field, and the light 
source remain intact and operating, UV would be emitted from the 
luminaire. It would therefore be advantageous that, in the event of 
breakage of the cover member to the luminaire, a means could be provided 
to insure that the light source is prevented from operating and emitting 
UV. One approach to solving this problem can be found in publications by 
Philips Lighting relating to their sports lighting luminaire identified as 
the "ArenaVision" luminaire. In this approach, a wire mesh grid is 
disposed within the glass material of the cover member similar to the type 
of safety glass previously utilized in commercial retail operations in 
doors and windows. Though effective for insuring the integrity of the 
glass cover and preventing the glass cover from scattering away from the 
open end of the luminaire, this approach has the adverse effect of 
blocking or obscuring the light output from the luminaire even when the 
cover is intact Furthermore, since this technique is directed to 
maintaining the positioning of the glass cover even in the event of 
breakage, rather than interrupting the operation of the light output, it 
could be possible that portions of the glass cover could be displaced 
resulting in some leakage of UV. It would therefore be advantageous if an 
approach could be used that would continuously monitor the integrity of 
the glass cover but at the same time, not obscure light output 
therethrough when the glass cover was intact under normal conditions. 
It can also be appreciated that if one took the approach of monitoring the 
condition of the glass cover so as to provide such condition as a logic 
input to the ballast arrangement used to power the light source, one could 
positively insure that the shutdown of the lamp operation under a broken 
glass cover condition, did occur. Therefore, not only would it be 
desirable to prevent the displacement of broken glass pieces by some means 
other than a light blocking wire mesh grid technique, it would also be 
beneficial to positively utilize the information that the glass has been 
broken as an operating input to the ballast arrangement of the luminaire. 
In providing a circuit control based on the condition of the cover glass, 
the cost of such an addition of logic elements, the number of components 
needed to perform this logic check, as well as the reliability of such a 
circuit would be of considerable importance. Therefore, it would be 
advantageous if a circuit to verify the integrity of the cover glass and 
thereby serve to insure the shutdown of the light source in the event of a 
broken glass condition, could be provided in an manner that was cost 
effective, used a minimum number of components and was extremely reliable 
in operation. 
SUMMARY OF THE INVENTION 
The present invention provides a sports lighting luminaire having broken 
glass detection arrangement which provides that in the event of a break in 
the cover glass which normally serves the purpose of filtering UV 
radiation, the ballast circuit arrangement which powers the light source 
will be disabled thereby preventing the emission of UV until the cover 
glass is replaced. The broken glass detection arrangement for the sports 
lighting luminaire of the present invention provides an integrity check of 
the cover glass without imposing any light blocking characteristics 
therewith. 
In accordance with the principles of the present invention, there is 
provided a luminaire having a reflector member with an open end and a 
closed end and wherein a high intensity light source is disposed near the 
closed end of the reflector member. A light transmissive cover member is 
disposed over the open end of the reflector member and is effective for 
filtering UV radiation emitted by the light source. The luminaire of the 
present invention includes a ballast circuit arrangement disposed in a 
ballast housing which can be connected to the reflector member. The 
ballast circuit arrangement includes an input portion receptive of line 
power and an output portion effective for conditioning the line power so 
as to provide conditioned power for energizing the light source. A 
conductor strip is disposed on the cover member and is effective so that, 
when the cover member is intact; that is, not broken, an electrical signal 
can be passed through the conductor strip. An interruption circuit 
arrangement is electrically coupled into the ballast circuit arrangement 
and is effective for interrupting current flow in the ballast circuit when 
the electrical signal through the conductor strip is detected as being 
absent thus indicating a broken glass condition. When the current flow in 
the ballast circuit arrangement is interrupted, the conditioned power 
generated in the ballast circuit arrangement is shutdown thereby 
effectively shutting down the operation of the light source and preventing 
any further emission of UV when the cover member is in a broken condition.

DETAILED DESCRIPTION AND OPERATION 
As seen in FIG. 1, the luminaire 10 having improved light delivery 
characteristics particularly suited for a sports lighting application and 
with the broken glass detection arrangement of the present invention 
includes an optical portion shown generally as 12, a ballast and ballast 
housing portion shown generally as 14 and a support arrangement 16. The 
support arrangement 16 physically connects the optical portion 12 to the 
ballast, housing portion 14. Additionally, the support arrangement 
connects to a mounting configuration 18 which serves the purpose of 
providing an adjustment means for setting the downward projecting angle of 
the luminaire 10 when in an installed environment. By separating the 
ballast portion 14 from the optical portion 12, a thermal isolation 
between such two portions is achieved. It should be recognized however, 
that the ballast portion 14 and optical portion 12 could be formed using 
an integral housing arrangement that utilized an alternate thermal 
isolation arrangement. Additionally, it can be appreciated that the 
ballast circuit arrangement could be disposed remotely from the optical 
portion; for instance, the ballast and housing therefor could reside at 
the base of a mounting pole with the optical portion at the top of the 
pole and electrically connected therebetween by means of conventional 
electrical cabling. It is contemplated that both such luminaire 
configurations would still be covered by the present invention 
particularly relative to the broken glass detection arrangement of the 
present invention. 
The optical portion 12 includes a reflector member 20 which can be 
constructed of a non-metallic material and is shown in the shape of a 
paraboloid of revolution. In the present invention, reflector 20 is 
constructed having a glass substrate material with a dichroic or multifilm 
interference coating disposed thereon. Other reflector configurations made 
of alternate materials could be utilized by someone skilled in the art and 
still practice the teachings of the present invention; for instance, the 
reflector could be elliptically shaped and it could be constructed of 
aluminum. In the preferred manner using the glass substrate and multifilm 
interference coating, the reflector member 20 can achieve reflectance of 
approximately 95% of the light generated by the light source as compared 
to the 75-85% value typically achieved using an aluminum reflector. With 
the parabolic Configuration of reflector 20, an open end 22 is formed at 
one end of the parabola, an apex end 24 is formed opposite the open end 
22, and a central axis extends therebetween. A cover member 26 is fitted 
over the open end 22 and secured to the reflector member 20 by means of a 
ring member 28. The cover member 26 is made of tempered glass and is 
effective for filtering unwanted UV radiation which is given off by the 
light source 30 disposed within the reflector member 20. The cover member 
26 can also be formed from a molded borosilicate material that would 
provide sufficient light transmissivity as well as avoidance of the 
shattering and spraying of broken glass pieces if the cover member is 
broken. 
The light source 30 is disposed within the reflector member 20 so as to be 
in close proximity to the apex end 24 of the reflector 20. The light 
source 30 of the preferred embodiment is a double ended, high intensity 
discharge (HID) lamp having a bare arc tube wall made of fused quartz and 
containing a metal halide fill which is excited to a discharge state 
thereby producing an elongated arc discharge within the arc tube. The 
light source 30 is disposed at a juncture point between the main reflector 
portion 20 and the rear reflector portion 20a so that, upon opening the 
rear reflector portion 20a, access can be had to the light source 30 from 
the rear. Of course, it can be appreciated that other light source types 
and orientations of such light sources relative to the reflector member 
can be utilized in conjunction with the broken glass detection arrangement 
of the present invention and it is contemplated that such modifications 
are within the scope of the present invention. 
As further seen in FIG. 1, disposed along the upper half of the reflector 
member 20 is a series of substantially equally spaced apart louver members 
32. These louver members 32 provide a means for redirecting light output 
that would otherwise exit the open end 22 at a large angle relative to the 
central axis, into a smaller such angle thereby allowing the lighting 
designer the ability to reduce glare or spill light from areas above the 
playing surface of the sports field. 
As seen in FIG. 2, the broken glass detection circuit arrangement 40 of the 
present invention, includes the cover member 26 from FIG. 1 as well as a 
conductive strip 42 which is shown disposed along the outer periphery of 
the cover member 26. The broken glass detection arrangement of the present 
invention could be equally effective wherein a protective jacket or cover 
over the light source 30 were utilized rather than merely a cover over the 
open end 22 of the reflector 20. The conductive strip 42 can be provided 
by means of a thin resistive material strip similar to that used for 
resistive heating on a automotive rear window defogger. However, in the 
present situation, because the conductive strip 42 is not intended to 
serve as a heating element and further because it is preferable that the 
conductive strip 42 not act to block light output through the cover member 
26, it would be sufficient to provide such conductive strip 42 as a very 
thin coating of such resistive material. The resistance of this conductive 
strip can be selected such that there is sufficient conductivitiy yet the 
size and thickness does not block light output; in this arrangement, the 
conductive strip was selected as having approximately 20 ohms resistance. 
This material is disposed in a thin layer and is brittle in nature so 
that, when the cover member 26 is broken, the conductive strip 42 will 
break as well. Furthermore, the conductive strip 42 is disposed preferably 
on the inner surface of the cover member 26 so that it is shielded from 
climate conditions and can therefore maintain a strong electrical coupling 
relationship with the rest of the circuit arrangement 40 over a prolonged 
period of time. It can be appreciated that although the conductive strip 
42 is shown disposed around the periphery of the cover member 26, it would 
be possible to dispose such conductive strip 42 in an alternate position 
and still achieve a breakage in the conductive strip 42 upon a breakage in 
the cover member 26. For instance, since the conductive strip 42 is a thin 
coating of the above described material and therefore will not serve to 
block light output from the light source 30, the conductive strip 42 can 
be disposed in a criss-crossing manner across the surface of the cover 
member 26. 
As further seen in FIG. 2, the ballast circuit arrangement 40 having the 
broken glass detection circuit 50 of the present invention includes a 
conventional auto-regulation transformer 46 and a ballast capacitor 74. Of 
course, it can be appreciated that other ballasting arrangements such as a 
convention transformer coupling configuration could be utilized in 
conjunction with the present invention. As illustrated in FIG. 2, the 
broken glass detection circuit 50 of the present invention is disposed on 
the primary side or input portion 44 of the auto-regulation transformer 46 
and as such, receives input power directly from input terminals 52. 
Disposed electrically adjacent one input terminal 52 is a fuse member 54. 
The fuse member 54 is sized so as to provide the circuit protection 
whereby, under conditions when the fuse member 54 is not bypassed as will 
be discussed hereinafter in further detail, a current in excess of a 
predetermined amount will be drawn through the input portion of the 
ballast circuit arrangement 40 for a specific period of time as would 
indicate the occurrence of a broken glass condition, resulting in blowing 
the fuse member 54. As an example, the fuse member 54 could be rated to 
blow at approximately 4 amps such that when a nominally rated current 
flows through fuse member 54 for a period of greater than approximately 
100 msecs, fuse member 54 will blow. Before the expiration of the 100 msec 
time duration, even in the presence of a substantially higher current, the 
fuse member 54 could not thermally react and therefore would not blow even 
upon initiation conditions wherein the ballast circuit arrangement 40 
draws an initial current pulse of up to 70 amps. Of course, it can be 
understood that these current valves are representational only and should 
not serve to limit the scope of the present invention. Other valves can be 
used depending on the lamp rating; it is only required that the current 
rating for the fuse 54 allow for a thermal delay as previously discussed. 
A resistor R1 is connected in series with fuse member 54 and has a 
resistive value selected so as to increase the voltage drop seen by a 
contact member 56. Connected in an electrically parallel relation to the 
fuse member 54 and resistor R1 is a contact member 56 which is associated 
with a relay coil 58. Resistor R1 raises the voltage drop across contact 
member 56 so that even in a situation where an oxide coating may have 
formed on the contact surfaces, there is sufficient voltage to ensure that 
current transfers from the fuse member 54 to the contact member 56 as soon 
as the contacts close. Contact member 56 is normally open so that when the 
relay coil 58 is not energized, current for the input portion 44 of the 
ballast circuit arrangement 40 will flow through fuse member 54. In this 
manner, upon initiation of the ballast circuit arrangement 40 wherein 
current has not yet flowed in the loop containing relay coil 58, current 
will initially flow through the fuse member 54 until such time as the 
contact member 56 is closed. Once the contact member 56 is closed by 
energization of relay coil 58, current will flow through the contact 
member 56 rather than the fuse member 54. Contact member 56 can be rated 
for example at approximately 16 amps and can react in approximately 16 
msecs. As previously discussed, since fuse member 54 cannot thermally 
react within 100 msecs of having a high current flowing therethrough the 
fuse member 54 is capable of handling the initial high current pulse 
whereas the contact member 56 cannot. After the drop-off of the initial 
current pulse, the contact member 56 essentially short circuits the fuse 
member 54 substantially before the expiration of the 100 msec time period. 
That is, since the contact member 56 is rated at 16 amps, by having the 
initial current pulse which can be up to 70 amps, flow through the fuse 
member 54 rather than the contact member 56, the contact member 56 is 
protected against welding as could otherwise occur in the presence of this 
high initial current pulse. In this manner the fuse member 54 and the 
contact member 56 cooperatively interact with one another so as to protect 
the other from damage due to current conditions associated with the 
respective initial conditions and continuous operations of ballast circuit 
arrangement 40. It should be appreciated that by using this type of 
cross-protection arrangement between fuse member 54 and contact member 56, 
the relay coil 58, contact member 56 device can be significantly reduced 
both in terms of size and cost as compared to the type of device that 
would otherwise have to be used if a relay contact were to be disposed in 
the input portion 44 so as to accommodate the high initial current pulse. 
For the contact member 56, relay coil 58 device of the present invention, 
it is possible to utilize a conventional low voltage, single pole relay 
available from either Potter Brumfield or Magnecraft as Model No. RKS-5DG 
or 76URCPCX, respectively, although other conventional relays would work 
equally as well. 
Relay coil 58 as illustrated in FIG. 2 as part of the broken glass 
detection circuit 50, is in series electrical connection with the 
conductive strip 42 a second resistor R2, a diode bridge 64 and the 
secondary winding 60 of a second transformer member 62. In this series 
circuit, the second resistor R2 is used to match the voltage output of the 
second transformer member 62 to the input voltage requirements of relay 
coil 58. Additionally, diode bridge 64 has been added to convert the AC 
output of the second transformer member 62 to full wave DC suitable for 
operating relay coil 58. A primary winding 64 of transformer 62 is 
disposed in the input portion 44 of ballast circuit arrangement 40. This 
second transformer 62 is effective for sensing current flow in the input 
portion 44 of ballast circuit 40 and inducing a current flow in the broken 
glass detection circuit 50 thereby energizing relay coil 58 when current 
is flowing in the input portion 44. It should be noted that the ratio of 
windings for the second transformer 62 is selected so as to result in a 
low voltage signal being developed within broken glass detection circuit 
50. The use of a low voltage signal thereby insures that arcing over does 
not occur as could otherwise occur in a high voltage condition for 
instance at point A as shown in FIG. 2. Use of the second transformer 62 
along with the relay coil 58 is also effective for isolating the broken 
glass detection circuit 50 from the input portion 44 of the ballast 
circuit arrangement 40; that is, with the contact member 56 and the 
primary winding 64 being disposed in the input portion 44 of the ballast 
circuit arrangement 40, the current flowing in input portion 44 is 
isolated from that which flows in the broken glass detection circuit 50. 
As a further condition to the continued energization of relay coil 58, the 
conductive strip 42 must remain intact thereby indicating that the cover 
member 26 has not been broken. In the event that the cover member 26 is 
broken resulting in the conductive strip 42 being broken, there is no 
longer continuity in the broken glass detection circuit 50 and the relay 
coil 58 will be de-energized thereby resulting in the opening of contact 
member 56. With contact member 56 open and current continuing to flow in 
the input portion 44 of ballast circuit 40, the magnitude of such steady 
state current flow in input portion 44 will be sufficient to blow fuse 
member 54 after the 100 msec. time period previously described. In this 
manner, the contact member 56 opens first so that the fuse member 54 
interrupts current flow rather than the contact member having to do so. 
Current flow in the input portion 44 is thereby interrupted resulting in 
the interruption of current flow through the auto-regulation transformer 
46 and the shutdown of light source 30. 
Following the shutdown of the light source 30 in the event of a broken 
glass condition, if one would attempt to restart the luminaire, it would 
be necessary to replace fuse member 54 as well as to replace the cover 
member 26; replacement of one such device without the replacement of the 
other would be ineffective toward the goal of restarting the luminaire 10. 
As seen in FIG. 3, the broken glass detection circuit 50 of the present 
invention is disposed in the output portion 48 of ballast circuit 40. The 
circuit arrangement 50 of FIG. 3 is identical to that of FIG. 2 except 
that the broken glass detection circuit 50 is energized off of the 
secondary winding of auto-regulation transformer 46 rather than through 
input terminals 52. Although the broken glass detection circuit 50 will 
function equally as well whether disposed in the input portion 44 or the 
output portion 48, it is to be appreciated that disposition in the output 
portion 48 is the preferred arrangement. This output side disposition 
allows for selection of component sizes and tolerances based only on the 
secondary current characteristics (as dictated by the wattage selected for 
lamp 66). If disposition on the input side were chosen, component values 
would change for the various nominal line voltage ratings at which the 
particular one lamp wattage could operate. 
Although the hereinabove described embodiment of the invention constitutes 
the preferred embodiment, it should be understood that modifications can 
be made thereto without departing from the scope of the invention as set 
forth in the appended claims. For instance, the values given for the 
current ratings on fuse member 54 and contact member 56 are exemplary only 
and are not intended to limit the scope of the present invention. It is 
contemplated that when the ballast circuit arrangement is altered in terms 
of energy output to accommodate a different wattage of light source, 
commensurate changes in the size and time response characteristics of the 
components illustrated in FIG. 2 can be made without departing from the 
scope of the present invention.