Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2001-08-31
2003-05-06
Pelham, Joseph (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S388000
Reexamination Certificate
active
06559425
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for the thermal treatment all friction lining surfaces, the friction lining surface being brought for a limited. To an elevated temperature. Moreover, the invention relates to the device for the thermal treatment off friction lining surfaces with a heating station for heating the friction lining surfaces.
2. Description of Related Art
A method and a device of the type mentioned above are known from EP 0 799 391 B1. They are useful for the treatment of surfaces of friction linings which are used especially in brakes of vehicles. Such friction lining surfaces generally contain organic binding agents. In order to prevent a so-called greenfading by the first use of a brake with a corresponding heat evolution, the friction lining surfaces are subject before fitting to a thermal treatment, the so-called scorching.
A known type of scorching consists in the treatment of the friction lining surface with a gas flame. However, the strong dependence of the temperature on the friction lining surface on the gas flame, especially on the composition of the used burnable gas and on the oxygen supply during the burning process, is disadvantageous. A too hot flame can result in melting the anorganic constituents or the metals in the friction lining surface; on the contrary, a cold flame can result in very long treatment periods or in the fouling of the friction lining surface.
Furthermore, according to the prior art, a scorching ensues by laying on or pressing a hot plate. Hereby, it can however come to a sealing of the friction lining surface during the contact with the hot plate. Moreover, the temperature of the hot plate can be maintained constant over the whole surface only with difficulty, and the bad heat conduction of the temperature stable high-alloy steels which are usually used has a negative effect on the heat transmission.
In the above mentioned EP 0 799 391 B1, the scorching also ensues by laying on a hot plate. In order to avoid a part of the problems related hereto such as especially the sealing of the friction lining surface and the nonuniform temperature distribution and to allow a timed operation, it is proposed to use several heating stations arranged the one behind the other in which the heating takes place stepwise. This method means high investment costs and high operating expenses. Moreover, the problem of a nonuniform heating of the surface basically remains and gas which originates at the time of the pressing-on cannot escape from the surface.
SUMMARY OF THE INVENTION
The aim of the invention is to improve a method and a device of the above mentioned type in such a way that this simple automatizable thermal treatment (scorching) of friction lining surfaces is possible at low cost and with a high-quality result.
This aim is achieved by a method according to which the increase in temperature of the friction lining surface takes place by infrared light irradiation and by a device having at least one infrared light source placed in the heating station.
Accordingly, the method for which the friction lining surface is brought to an elevated temperature for a limited period in a known manner is characterized in that the increase of temperature takes place with an infrared light irradiation. Various important advantages can thus be obtained. On the one hand, the heat supply can be exactly controlled. Thus, the friction lining surface can be heated very uniformly and very exactly to the desired temperature. On the other hand, no parts have to be in contact with the friction lining surface. The gas eventually developing on the friction lining surface because of the heating can thus freely escape from the surface and do not cause any damages. The medium surrounding the friction lining surface can also be freely chosen so that for example atmospheres with a certain effect can be adjusted to the friction lining surface. Not least the use of infrared light also causes lower investment and operating expenses. The minor susceptance to failure, the automatizability of the method as well as the energy saving also contribute to reduce the operating expenses, since due to the infrared light the heat energy can be brought exactly and without high losses to its place of activity. Reduced investment costs result from a mechanical assembly which is considerably simplified.
The infrared light used advantageously has a wavelength of 780 to 1400 nm, the maximum of intensity being preferably at 1200 nm. Thus it is preferably short-wave infrared radiation. The advantage of the short-wave infrared radiation is that this radiation transports the heat energy very efficiently and without a medium. The heating of the friction lining surface can thus also take place under depression and the removal of the decomposition products from the anorganic constituents of the friction linings which arise during scorching can be carried out with strong suction devices without impairing the heat transport of the infrared light sources to the friction lining surface. A further advantage of the short-wave infrared radiation is that the infrared radiators used for this purpose have a very short reaction time of 1 to 3 s so that the scorching installation does not have to be continuously working and must only be switched-on on demand, i.e. for the actual scorching process in order to obtain the temperature necessary for the work cycle.
The friction lining surface can be irradiated with an infrared light power density of 150 to 800 kW/m
2
. For these values, the friction lining surface is heated quickly. However this takes place without coming to damages because of local overheating or without the heat being distributed nonuniformly on the surface.
The increase of temperature takes place preferably up to a temperature of 600 to 900° C. in order to guarantee an optimal scorching.
The irradiation of a friction lining surface advantageously takes place for a period of 5 to 40 s, preferably for 25 to 35 s. Such values guarantee on the one hand a gut result of treatment, on the other hand the treatment is carried out quickly and thus allows an automatized production. Hereby, attention must be paid to the fact that for example in comparison with EP 0 799 391 B1 basically only an unique heating step is necessary. In case it is desirable for some reason, a multistage heating could naturally also take place by correspondingly driving or arranging the infrared light sources.
The friction lining surface can be transported during the irradiation along the infrared light source what preferably takes place at a speed of 1,0 to 2,0 m/min. The production process can thus take place continuously and with a known speed, and the infrared light sources do not have to be continuously alternately switched on and off. Moreover, a thermal treatment during the transport has the advantage that eventual non-homogeneities in the radiation field of the infrared light sources are compensated, since the friction lining surface is moved in the radiation field.
The friction lining surface is preferably cooled down after irradiation. Thus, among other things, the quick further processability of the friction linings is made possible.
In a further development of the method, the thermal treatment is carried out in an inert oxidizing reducing or in a depression atmosphere. Desired properties of the friction lining surface can thus be specifically influenced. The selection of the atmosphere can take place entirely with respect to the desired result, since the infrared light irradiation hardly imposes restrictions with respect to the usable atmosphere types. According to the prior art, a supporting use of such atmosphere types was not possible, neither during heating with flames, nor with hot plates.
The temperature of the friction lining surface will be measured and the treatment process will be controlled in dependence hereupon. Since the friction lining surface is always freely accessible during the thermal treatment—differently from the prior art—a temperature measurem
AlliedSignal Bremsbelag GmbH
Kueffner Friedrich
Pelham Joseph
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