Center high mounted stoplight

A central high mounted stoplight arrangement for a motor vehicle that utilizes an optical prism coupler mounted on the rear deck lid at the center thereof for receiving and projecting light rays to the rear of the vehicle.

This invention concerns vehicle brake lights and more particularly relates 
to a so-called center high mounted stoplight which in the last few years 
has been required to be placed on U.S. motor vehicles. 
At times it is desirable for styling purposes to install a center high 
mounted stoplight directly on the truck lid rather than behind the vehicle 
back-lite. Placing the stoplight on the deck lid, however, can create some 
problems not the least of which is accessibility to the light bulb if the 
latter should burn out. Wire routing to the stoplight bulb on the deck lid 
can also be a problem because of the usual two-piece construction of the 
deck lids not providing suitable passageways for easily feeding the wires 
to the light bulb. 
Accordingly, the present invention is directed to a center high mounted 
stoplight for use with the deck lid of a vehicle that provides a simple 
and low cost solution to the above problems. Simply stated, the present 
invention utilizes a conventional stoplight that is installed in the trunk 
adjacent the rear bumper of the vehicle in a manner so that the light beam 
is directed vertically upwardly. In addition, an optical prism coupler is 
mounted in the center of the deck lid and serves to intercept the light 
beam emanating from the stoplight and redirects the light beam 
horizontally in a rearward direction. 
The objects of the present invention are to provide a new and improved 
stoplight arrangement for a motor vehicle that utilizes an optical prism 
coupler mounted on the deck lid for receiving and projecting light rays to 
the rear of the vehicle; to provide a new and improved center high mounted 
stoplight for a motor vehicle in which the stoplight assembly is mounted 
in the trunk so as to provide a vertically directed beam which is 
intercepted by an optical element supported by the rear deck lid and 
redirected horizontally rearwardly of the motor vehicle; to provide a new 
and improved center high mounted stoplight for a motor vehicle in which a 
reflector element is mounted in the deck lid at a rear portion thereof and 
receives a beam of red light from a light source located within the trunk 
adjacent the bumper of the motor vehicle; and to provide a new and 
improved warning light arrangement for a motor vehicle in which a movable 
closure member of the vehicle supports a reflective member which receives 
a beam of light from a light source mounted in a fixed position within the 
vehicle.

Referring now to the drawings and more particularly FIG. 1 thereof, the 
rear end of a motor vehicle 10 is shown which includes the usual trunk 12 
for carrying luggage and the like. The trunk 12 consists of a compartment 
14 defined by the body structure of the vehicle such as the laterally 
spaced rear fenders (one of which is shown and identified by reference 
numeral 16) a rear body panel 18 which extends transversely of the 
vehicle, a floor pan 20, the rear part of a seat back 22, and a deck lid 
24. As is conventional, the deck lid 24 is supported by hinge means (not 
shown) for pivotal movement above a horizontal axis between the closed 
position shown in full lines and an open position shown in phantom lines. 
A center high mounted stoplight 26 is incorporated with the trunk 12 in 
accordance with the present invention and, in the preferred form, includes 
a light source 28 mounted within the compartment 14 and an optical prism 
member 30 which is carried by the rear portion of the deck lid at the 
center thereof. The optical prism member 30 is triangular in cross section 
and is defined by sides A, B and C. Sides A and C intersect at an angle of 
90.degree. while sides C and B, and A and B each intersect at an angle of 
45.degree.. More specifically, the light source 28 is fixed to the inner 
surface of the panel 18, which in turn, is located above the rear bumper 
32 of the vehicle 10. The light source 28 includes a housing 34 which 
supports a parabolic reflector 36, a light bulb 38, and a lens 40 which 
normally would be colored red. The light bulb 38 is intended to be 
energized whenever the brake pedal of the vehicle 10 is depressed so as to 
indicate to a following vehicle that the vehicle brakes are being applied. 
Also, the reflector 36 is positioned so that the light rays emanating from 
the light bulb are directed upwardly towards the optical prism member 30. 
Thus, when the deck lid 24 is closed and the brakes are applied by the 
vehicle driver, the light rays of the light bulb 38 are directed by the 
reflector 36 through the colored lens 40, and as seen in FIG. 3, the 
colored light rays then enter the optical prism member 30 at side A as 
indicated by the arrow 42 and are redirected by the inclined side B of the 
prism member 30 through side C in a rearward horizontal direction as 
indicated by the arrow 44. 
The condition for total internal reflection of the light rays by the 
optical prism member 30 requires that the incidence angle .theta. which in 
this case is 45.degree., must exceed the critical angle .theta..sub.c 
given by the equation 
##EQU1## 
where .eta..sub.1 is the index of refraction of the surrounding medium (in 
this case air) and .eta..sub.2 is the index of refraction of the coupler 
medium. For example, if the prism 30 is made from a plastic material such 
as polymethylmetacrylate where .eta..sub.2 .perspectiveto.1.49, then 
.theta..sub.c will equal 42.1.degree.. If polycarbonate is used as the 
material for the prism 30, then .eta..sub.2 =1.59 and .theta..sub.c 
=39.degree.. Thus, the incidence angle (45.degree.) of the prism 30 would 
exceed the critical angle in both cases and provide the total internal 
reflection desired. 
As seen in FIG. 1, the prism 30 when viewed from side C is generally 
rectangular in configuration and is surrounded by and supported within a 
rectangular opening 46 formed in the deck lid 24 by a flexible urethane 
adhesive or other flexible means and also suitable support means (not 
shown) so as to permit the prism member 30 to absorb vibrations and shocks 
during movement of the vehicle and when the deck lid is closed. 
Various changes and modifications can be made in this construction without 
departing from the spirit of the invention. Since such changes and 
modifications are contemplated by the inventors, they do not wish to be 
limited except by the scope of the appended claims.