GB2183130A - Heated rearview mirror - Google Patents

Abstract

The present invention refers to a process for manufacturing rearview mirrors provided with electrical heating. A film of a resistive conductor metalic material is metalized upon one surface of a sheet of glass, this metalized film being connected to an electrical power source in order to simultaneously act as a reflective surface and as a heating element for the mirror, thus dispensing the use of separate heating elements as well as temperature control devices.

Description

SPECIFICATION Process for Manufacturing a Rearview Mirror and Rearview Mirror The present invention refers to rearview mirrors in general and, more particularly, to a rearview mirror provided with an electrical heating system.

Several electrically heated rearview mirrors are known to the art, the heating being used to prevent the reflective surface of the mirror from clouding as a result of moisture, mist, fog and/or frosting of the mirror during days of more intense cold.

Typically, rearview mirrors are electrically heated, by resistive heating elements formed from copper, nickel-chrome and other alloys, which are sandwiched between films of flexible plastic material provided with adhesive to secure the heating element to the mirror glass, the terminals or contacts thereof for power supply being welded, riveted or reinforced with adhesive.

However, mirrors manufactured according to this process present serious inconveniences. For example, the plastic materials and adhesives are generally attacked by the heat generated in the heating element and deteriorate with time. In addition, the attaching of the terminals to the flexible plastic material is worksome and does not always ensure proper insulation, whereby there is a permanent risk of water infiltration, which may attack the adhesives and the heating element.

Furthermore, the fact that the heating element is sandwiched between films of plastic materials causes the consumption of power to be higher than necessary, because part of the heat generated thereby is dispersed throughout the plastic before reaching the glass.

Another type of widely used heated rearview mirror has its heating element comprised by wires of resistive material isolatedly pressed onto an aluminium foil which is fastened to the surface of the glass with self adhesive tapes. However, due to the clearance between the heating element and the glass, this type of mirror presents the same problem of excessive power consumption as the previously discussed mirrors.

A third type of electrically heated rearview mirror has its heating element formed by the application to the surface of the glass of a conductive paint which, after being cured, receives the power supply terminals, a thermal device and a bimetallic circuit breaker, the purpose of which is to control and maintain the temperature within a certain range, these elements being welded to the conductive paint, after which a layer of adhesive is applied thereto.

However, this type of electrically heated mirror also presents inconveniences, which begin with the difficulty in applying the adhesive, that does not manage to follow the irregularities of the welding, go on to the deterioration of the adhesive due to the action of heat, and end with great risk of failure or breakdown of the electromechanical control devices due to the vibration to which they are submitted.

Brazilian patent application number Pl 8502319 filed on May 13, 1985 by the same applicant discloses a process for manufacturing electrically heated rearview mirrors which eliminates most of the above discussed inconveniences of the prior art.

According to that patent, which specification is hereby incorporated as a reference, a silver based conductive paste is silk-screened upon one surface of the mirror and hardened on a high temperature oven.

However, even the above mentioned process presents serious inconveniences. For example, submitting the mirror to a high temperature may cause its cracking or may temper it, as well as it may compromise its plane condition. Additionally, it is very difficult to apply the silver based conductive paste to a non-planar surface.

The object of the present invention is to provide a solution for these inconveniences of the prior art by providing a process for manufacturing a rearview mirrorwith an electrical heating system which is easy to achieve, easy to manufacture, very reliable and presents a very low power consumption.

According to the present invention, this object is attained by providing a process for manufacturing a rearview mirror having an electrical heating system characterized by comprising the steps of: vacuum metallizing a film of a resistive conductor metallic material upon one surface of a sheet of glass, and connecting said metallized resistive film to an electrical power source, whereby said resistive film simultaneously acts as a reflective surface and heating element.

The present invention shall now be described in greater detail from a exemplary but not limiting standpoint, in order to facilitate its understanding.

According to the present invention, a process for manufacturing a rearview mirror basically comprises the following steps.

The sheets or blades of glass to be processed, having a predetermined thickness, are submitted to a previous washing operation in a machine or device suitable for this washing, from which the already washed sheets of glass are properly prepared for the metallizing operation.

The preparation for the metallizing operation is basically divided in two steps: preparing the sheets of glass and preparing the metallizing machine. The sheets of glass are housed on suitable support means of the metallizing machine, while the machine is fed with the material to be metallizing, preferably alloys having a low melting points placed upon tungsten filaments.

After the machine has been fed with the tungsten filaments and the metallizing material, the support means housing the pre-washed sheets of glass are introduced in the metallizing machine, which is then heretically closed and actuated. With the actuation, vacuum is created in the interior of the machine, up to pressure of about 10-4 atmospheres, which indicates the metallizing of the glass through the sublimation of the metallic alloy having a low melting point, which completely evaporates and is deposited on the substrate (sheet of glass) in the back surface of the mirror.

When this operation is finished, the interior of the metallizing machine is returned to room pressure through the injection of air, in order to allow the removal of the metallized sheets of glass, which takes about 10 minutes.

With the metallizing machine open, the support means housing the duly metallized sheets of glass are removed from the machine and transported to the following step of the process, where the sheets are cut into the desired final shape for each mirror.

Afinishing and protective mask, preferably formed from a neutral organic material is then applied over the cut mirrors, which masks are formed with two open slots along its sides adjacent to the extremities of each mirror, these slots defining open areas on the metallized surfaces which will later receive the electrical terminals of the mirror.

The electrical terminals which connect the metallized surface to the electrical system of the vehicle are welded to the metallized surface, this welding operation using a non-ferrous alloy as adding material and a flux which provides better adherence and facilitates the flowing of the adding material, providing a better finishing.

Following the application of the adding material on the open areas defined by the slots, the electrical terminals for connecting the mirror are positioned and the basic structure of the mirror is completed.

Additionally, a second layer of finishing and protective material also from a neutral organic material may be applied over the finished mirror.

The mirrors manufactured according to the process above described, besides solving the several above discussed inconveniences of the heated rearview mirrors known to the art, provide a substantial reduction in the manufacturing costs of these electrically heated rearview mirrors, since the individual heating elements are eliminated.

In fact according to the present invention, the simultaneous use of the metallized film as a reflective surface and as a heating element represent not only a substantial reduction in the consumption of power, because there are no heat losses, but also a better performance of the mirror since all its surface area is evenly heated.

The metallized film can be formed from several metallic materials, such as nickel/chrome, copper, silver, aluminium or its alloys, the thickness of the layer being projected as a function of the physical characteristics of each metal or alloy (resistivity) in order to generate only the amount of heat necessary to uncloudthe mirror. This projecting of the thickness of the metallized film additionally allow the elimination of thermostats or any other temperature control means, since this system allows the temperature of the mirror surface to reach a perfect balance of temperature without any loss of heat.

The present invention having been described, it should be understood that the invention is subject to several modifications in its forms of presentation, provided that any of such modifications do not depart from the spirit and scope of the following

Claims (10)

claims. CLAIMS

1. Process for manufacturing a rearview mirror provided with electrical heating, characterized by comprising the steps of: vacuum metallizing a film of a resistive conductor metallic material upon one surface of a sheet of glass; and connecting said metallized film to a power source, whereby said metallized film simultaneously acts as a reflective surface and as a heating element.

2. Process according to claim 1, characterized in that said metallized film is formed by any metal selected from the group consisting of copper, nickel, stainless steel, chrome, aluminium, silver and its alloys.

3. Process according to claim 1, characterized in that said metallized film is metallized on the back surface of the mirror.

4. Process according to claim 1,further characterized by comprising the step of washing said sheet of glass prior to the step of vacuum metallizing.

5. Process according to claim 1, further characterized by comprising the step of applying a first layer of organic material protective paint over said metallized surface.

6. Process according to claim 5, characterized in that said step of applying a protective paint includes the formation of two open slots on said metallized surface for the connection of electrical terminals.

7. Process according to claim 6, further characterized by comprising the step of applying a second layer of organic material protective paint over said connected electrical terminals.

8. Rearview mirror provided with electrical heating, characterized by comprising a sheet of glass having a metallized film formed from a resistive conductor metallic material upon one of its surfaces, said metallized film being connected to a power source and simultaneously acting as a reflective surface and as a heating element.

9. A process for manufacturing a rearview mirror provided with electrical heating, substantially as hereinbefore described.

10. A rearview mirror provided with electrical heating, susbtantially as hereinbefore described.