JPS63204201A - Front lens for lighting fixture for signal - Google Patents

Abstract

PURPOSE:To improve visibility by sectioning a lens surface into sectorial parts with concentric circles and plural radial radii and providing Fresnel prism elements to the respective sectorial parts. CONSTITUTION:A reflector 3 is provided in a lamp housing 2, a light source bulb 4 is provided nearly its focus, and a front lens 1' is mounted covering the front surface opening part of the lamp housing 2. Five concentric circles 1a-0-1a-4 are set on the surface of the front lens 1' and 20 radial radii 1r-1-1r-20 are set, so 80 sectorial parts are formed except in the circle 1a-4 and Fresnel prism elements are provided to the sectorial parts respectively. Further, the part inside the smallest concentric circle 1a-4 is painted out with black opaque paint and the entire shape of a light emission surface is formed in a ring shape. Here, a section E shows an area where one Fresnel prism element is arranged. Consequently, plural parts on the front lens illuminate intensely and the visibility is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a front lens of a lamp used for a signal, such as a brake light for an automobile.

[Conventional technology]

This type of signal light generally has a structure in which a concave mirror is provided within the lamp housing.

The above concave mirror may be constructed separately from the lamp housing, or a reflective coating may be provided on the inner surface of the lamp housing.

A light source bulb is installed near the focal point of the concave mirror, and a front lens is attached to cover the front opening of the lamp housing.

Conventionally, the above-mentioned front lens is generally provided with a fine fisheye prism uniformly provided on the entire surface. Here, "fine" means that the size is such that a person with normal vision cannot distinguish each fisheye prism element from a viewing distance under normal usage conditions.

[Problem that the invention seeks to solve]

For example, in the case of a signal light such as a lighthouse that is visible from a distance of several kilometers, the visibility of the signal light is mainly determined by the luminous intensity, one color tone, and the directionality. However, in the case of a signal light such as a brake light that is visible from a relatively short distance of several meters to several tens of meters, the luminous intensity distribution on the front lens surface is also a major factor.

According to the inventor's experiments, a light distribution characteristic in which a plurality of points on the front lens surface shine brightly provides a better visual recognition effect than when the front surface of the signal light emits light uniformly.

Applying the prior art to make a plurality of points on the front lens shine brightly, a front lens as shown in FIG. 4 can be considered (hereinafter referred to as a "proposal").

Figure 4 (A) is a rear view of the prototype front lens, Figure 4 (B)
) is the BB sectional view.

The front lens l of this prototype has a circular shape, and its surface is surrounded by four concentric circles 1. -I~1. -4 and 20 radial radii 1
r-+, L-2 to 1r-2°, 40 fan-shaped portions are defined, each of which has a fisheye prism element 1.
20 each of b-+, 'Ib-□, 1b-s, and 1ゎ-4 are provided.

As can be easily understood from the above configuration, the above five types of fisheye prisms are lb-+ + 1b-t + 1
It becomes smaller in the order of b-3+1b-4. Therefore, in order to make the exit angles of these fisheye prism elements the same, it is necessary to change the radius of curvature of each fisheye prism element.

For this reason, if the radius of curvature of adjacent fisheye prism elements is different, the following technical difficulties arise.

FIG. 5 shows a part of the mold 5 for injection molding the fisheye prism lens of this prototype. 5a and 5b are concave spherical surfaces having different radii of curvature.

Since the radii of the two concave spherical surfaces 5a and 5b are different, a step 5c is formed at the boundary thereof.

The above-mentioned step 5c makes injection molding of the prism lens difficult, and when the front lens 1 of the prototype is viewed from an oblique direction, the step formed by the step 2c appears in the shadow, making it difficult to manufacture the prism lens. Lose value.

The present invention has been made in view of the above-mentioned circumstances, and has the following features: (1) multiple points on the front lens surface shine strongly, providing good visibility; and (ii) injection molding is possible because there is no step between adjacent prism elements. It is an object of the present invention to provide a front lens for a signal lamp that is easy to use and (iii) has no shadow even when viewed from an oblique direction because there is no step.

[Means for solving problems]

In order to achieve the above object, the front lens of the present invention is a front lens that is attached to cover the front opening of the lamp housing of a signal lamp in which a concave mirror is provided in the lamp housing and a light source bulb is installed near the focal point of the concave mirror. The lens surface is divided into fan-shaped parts by concentric circles and a plurality of radial radii, and a Fresnel prism element is provided in each of the fan-shaped parts. As a result, each Fresnel prism element forms a "distributed light spot" and stands out, improving visibility.

The center position of the concentric circles can be set arbitrarily. Moreover, multiple sets of concentric circles having multiple centers can also be provided.

The above-mentioned radius means the radius of the above-mentioned concentric circles.

Furthermore, it is not necessarily necessary to provide Fresnel prism elements in all of the divided fan-shaped portions; in particular, it is not necessary to provide Fresnel prism elements on the inside of the smallest circle among the concentric circles. It is not necessary to set it well.

[For production]

According to the above configuration, the front lens surface is neatly partitioned, making it easy to arrange the prism elements, and furthermore, since Fresnel prism elements are used as the prism elements, there are no steps between adjacent prism elements.

Since there are no steps between the prism elements, injection molding is easy, and when the lamp using this front lens is viewed from an oblique direction, no shadows are visible at the boundaries between the prism elements.

〔Example〕

21iJ (A) is a sectional view of a signal lamp using one embodiment of the front lens according to the present invention, and FIG. 2(B) is an enlarged detailed view of part B thereof.

FIG. 1 is a rear view of the above-mentioned signal lamp.

As shown in FIG. 2(A), a reflector 3 is provided within the lamp housing 2, and a light source bulb 4 is provided near the focal point of the reflector 3.

A front lens 1' is attached through the front opening of the lamp housing 2.

As shown in Fig. 1, five concentric circles 1. -6) 1m-1+ 11-2 + 1.
-3 +18-4 is set, and 20 radial radii of 1□I to 1□2° are set. As a result, 1 yen
80 fan-shaped parts are formed except for 3-4.

A Fresnel prism element is provided in each of the sector-shaped portions. Inside the smallest concentric circle 1m-4 (shown with spots)
is filled with black opaque paint. In this way, in this embodiment, the overall shape of the light emitting surface is formed into a ring shape.

Section E shown in FIG. 2(B) represents an area in which one Fresnel prism element is disposed.

FIG. 3 shows a part of the mold 6 for molding the above-mentioned front lens 1'', and is a partial perspective view corresponding to FIG. 5 of the above-mentioned draft plan. This is the negative surface of the Fresnel prism element, and there is no separate step between the two.

Therefore, injection molding is easy, and when this front lens l° is viewed from an oblique direction, no shadow is perceived between the Fresnel prism elements.

FIG. 6 shows a different embodiment from the above. The front lens 7 of this example is constructed by canting the top and bottom, left and right sides of the front lens 1 of the previous example, so that the entire ring part has a shape similar to a rectangle. Even in this case, the same operation and effect as the previous example can be obtained.

〔Effect of the invention〕

As described in detail above, when the present invention is applied, (i) multiple parts of the front lens surface shine strongly and visibility is good, and (ii) injection molding is easy because there is no step between adjacent prism elements. (iii) Since there is no step, there is no shadow even when viewed from an oblique direction, which is an excellent practical effect.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a rear view, FIG. 2 is a sectional view, and FIG. 3 is a partial perspective view of a molding die. Figures 4 and 5 show the prototype front lens, and Figure 4 (
A) is a rear view, Fig. 4 (B) is a sectional view taken along line B-B, and Fig.
The figure is a partial perspective view of a molding die. FIG. 6 is a rear view of an embodiment different from the above. 1.1°...Front lens, 2...Lamp housing, 3...Reflector, 4...Light source bulb, 5.6.
...Mold, 7...Front lens.

Claims (1)

[Claims] In a front lens attached to cover the front opening of the lamp housing of a signal lamp in which a concave mirror is provided in the lamp housing and a light source bulb is installed near the focal point of the concave mirror, the lens surface is defined by a concentric circle and a plurality of radial radii. A front lens for a signal lamp, characterized in that the front lens is divided into fan-shaped parts, and a Fresnel prism element is provided in each of the fan-shaped parts.