Apparatus For Outdoor Lighting, Especially For Traffic Signs

Abstract

An outdoor lighting fixture having a high discharge lamp which requires a relatively high feeding voltage. The fixture is supplied with mains voltage by a cable located in the ground. A first transformer located below the ground is used to step-down the high voltage from the mains. The resulting low voltage is transmitted to a second transformer which steps-up the voltage to that required by the lamp. This second transformer is located adjacent to and is connected to the lamp.

Parent Case Text

The present application is a continuation of copending application Ser. No. 152,348 filed June 11, 1971, now abandoned.

Description

The present invention relates to outdoor lighting, especially illuminated traffic signs, sign posts, and the like being located in such a manner, that they can be driven into by vehicles.

In order to obtain a satisfactory illumination of such signs the light must be of high intensity and suitably also showing a spectral characteristic similar to that of the day light. Both for reasons of security and economy the source of light must have a long life. Sources of light, meeting these requirements, are for example luminous discharge lamps, especially mercury vapour discharge lamps.

However, luminous discharge lamps require a relatively high feeding voltage, which means that in case a lighting apparatus of the initially mentioned type is provided with a luminous discharge lamp, is driven into by a vehicle and damaged, the material of the lighting apparatus might be alive with electricity of a voltage dangerous to life.

The purpose of the present invention is to provide an apparatus for outdoor lighting of the mentioned kind, which apparatus does not include this latent risk to road users and service men.

Accordingly, the present application relates to an apparatus for outdoor lighting, especially for traffic signs, sign posts, and the like being located in such a manner that they can be driven into by vehicles and being provided with a source of light, especially luminous discharge lamps, that requires a relatively high feeding voltage and which lamps are being fed with mains voltage by a cable located in the ground and further having the actual lighting mounting placed on a column, pole or the like, preferably extending from a ground foundation. According to the invention such an apparatus is characterized by a first transformer, formed as a transformer having a primary and secondary wiring and step-down transformation, said transformer being supplied with mains voltage to the primary side thereof, and further having a very good isolation between the primary and secondary sides and on the secondary side having a physiologically harmless voltage, preferably in the order of 15 - 30 volts and in any case not exceeding 48 volts of open circuit voltage, and which transformer is mechanically protected against any collisions with vehicles and via lines from the secondary side thereof being in connection with the input terminals of a step-up transformer. The latter transformer being arranged in immediate connection to the actual lighting mounting and provided in order to step up the physiologically harmless voltage to the voltage required to illuminate the source of light. Firstly, by such an apparatus no voltages dangerous to life can be formed between the material of the lighting apparatus and the ground. Secondly, repair and maintenance of the lighting apparatus can be accomplished easily and with complete safety and consequently service men and installation contractors need not have competence for such tasks.

The invention will be further described in the following description with reference to the drawings, in which

FIG. 1 shows an outdoor lighting apparatus and

FIG. 2 illustrates a circuit diagram for a lighting apparatus according to the invention.

The full transformer 1 having an isolation of 4 kV, is being supplied with mains voltage to the primary side 2 thereof by a wire located in the ground. A choke coil 3 can be connected in series with the primary side of the transformer 1 in order to give the correct voltage current characteristic for feeding the luminous discharge lamp. Alternatively, the transformer 1 can be constructed as a leakage flux transformer in such a way that it is showing reactor characteristics in itself.

The transformer 1 and optionally the choke coil 3 together with fuses, switches and similar (not shown) are combined as a unit, referred to as a feeding device 4. The feeding device 4 is arranged in a mechanically protected manner in the ground or in a ground foundation, not shown, so that the feeding device can not be mechanically damaged by collision with a motor vehicle.

The transformer 1 is on the secondary side 5 thereof providing a low voltage in the order of 15 - 30 volts, this is a physiologically harmless voltage that in any case, considering current rules, should not exceed 48 volts. From the secondary side 5 of the transformer 1 a pair of coils conduits 6, 6' are leading to the actual mounting 7, for example placed in the top of column or pole, not shown. The mounting 7 includes a second transformer 8, suitably consisting of a full transformer having a luminous discharge lamp 9, as illustrated, for example a Hg-lamp or a Na-lamp connected to the secondary side thereof. The transformer 8 is a step-up transformer and the output side thereof is provides a high voltage, suitable for driving the lamp.

The transformer 8 is preferably placed in immediate connection to the mounting for example within a covering for the mounting.

In case the covering for the mounting is formed of a strong, isolating plastic material the transformer 8 can be wrapped in this covering and be constructed as an auto transformer.

The feeding device 4 is suitably, not shown, made short-circuit proof, either by the transformer 1 having such a character that the secondary side thereof without risk of damaging the transformer can be short-circuited and/or by connecting a thermal fuse to the primary circuit of the transformer 1. Such steps are known per se and obvious to those skilled in the art and consequently will not be further described in the specification.

In case the feeding device is made short-circuit proof all the work on the secondary side thereof and in the mounting can be made having the secondary short-circuited for example using a switch or a clamp making the apparatus short-circuited, thereby further reducing the risk for service men and installations contractors.

In summary the feeding device 4, being positioned into the ground and thereby protected, has the following functions among others:

It galvanically differs the a.c. mains from the actual mounting so that the mounting in this respect is completely safe to touch.

Further, the mains voltage should be transformed down to a physiologically harmless voltage, which according to the rules must not exceed 24 volts of open circuit voltage.

The feeding device 4 should be of such a construction and arranged in such a manner that the low voltage can be short-circuited, i.e., either provided with a depending or undepending short-circuit fuse.

Further in the illustrated embodiment the feeding device 4 provides the required choke coil characteristics to the low voltage for feeding Na or Hg-lamps, either by connecting a choke coil in series with the primary side of the transformer or by using a so called leakage flux transformer as the transformer including the required choke coil character in itself.

However, within the scope of the invention the choke coil function can be moved to the actual mounting, for example by providing a choke coil, not shown, on the secondary side of the transformer 8 or by constructing the transformer 8 as a leakage flux transformer.

Naturally, these and similar modifications lying within the scope of the knowledge of the person having average skill in the art could be made without departing from the present invention, as claimed in the following claims.

Claims

I claim:

1. In an outdoor lighting apparatus, comprising a high voltage light source, a vertical lamp post, ground foundation means supporting said lamp post, first transformer means protectively located inside said ground foundation means, second transformer means located near the top of said lamp post in close proximity to said high voltage light source, a main voltage underground cable connected to a primary winding of said first transformer means, first connecting means inside said lamp post and connecting a secondary winding of said first transformer means to a winding of said second transformer means, and second connecting means connecting a winding of said second transformer means to said high voltage light source, the improvement consisting of said first transformer means being a step down transformer wherein said primary winding is completely and safely insulated from said secondary winding, the induced voltage in said secondary winding being typically from 15 to 30 volts and not above 48 volts and said second transformer means being capable of transforming low induced voltage to the high voltage required for said high voltage light source.