Method to separate silicone seal by thermal degradation

Details Method to separate silicone seal by thermal degradation Method to separate silicone seal by thermal degradation

2003-10-14

2004-10-19

Carrillo, Sharidan (Department: 1746)

Cleaning and liquid contact with solids

Processes

Including work heating or contact with combustion products

C134S002000, C134S017000, C134S025200, C134S034000, C134S035000, C134S042000, C126S0010AA, C126S0390BA, C126S0390BA, C126S211000, C126S217000

Reexamination Certificate

active

06805753

ABSTRACT:

BACKGROUND
Silicone sealants are used to form a watertight seal around glass-ceramic cooktops for the appliance industry as shown in FIG.
1
. The silicone sealant
12
is dispensed around the cooktop
10
between the glass-ceramic cooking surface
14
and the frame
16
and prevents water from seeping under the cooktop and damaging the electrical components. The sealant also acts as an adhesive to bond the glass-ceramic cooking surface
14
to the frame
16
. Since the seal is visible to the consumer, it must be smooth, uniform and free from defects.
During the assembly process, some of the cooktops do not meet the quality requirements due to uneven, torn seals or inadequate sealant. In order to lower the overall manufacturing cost, units with defective seals may be salvaged. It is also possible to salvage parts of the appliances which are damaged during the assembly, shipping, and handling processes, either internally or externally at the manufacturing facility. In all reject cases, the glass-ceramic top is preferably re-used in a new assembly in order to save costs, since the glass-ceramic is generally the most expensive component. The porcelain or plastic frame is discarded as is the sealing material. In order to re-use the glass-ceramic cooktop, it must be cleaned and free of all foreign materials such as sealant. Cured sealants are very strong and difficult to remove. The current method of cleaning the cured sealant from the glass includes cutting out the seal by running a blade along the length of the cooktop against the glass. The glass-ceramic is separated from the frame by inserting a knife blade between the backside of the glass and frame, and cutting along the length.
The current procedure is risky in that the knife could scratch the glass-ceramic material. Scratches on the backside of the glass-ceramic weaken it, leaving it susceptible to breakage later. Even scratches too small for the technician to see can weaken the strength of the glass-ceramic. A further problem in using a knife to clean the surface of the glass-ceramic is the possible safety hazards associated with this operation.
SUMMARY
The present invention provides a method for removing silicone sealant from glass-ceramic surfaces. The method includes heating the sealant to a temperature greater than 325 degrees Celsius and then, preferably, mechanically removing the sealant from the glass-ceramic surface.
The present invention further provides a method of salvaging a glass-ceramic cooking surface from a cooktop including silicone sealant between a frame of the cooktop and the glass-ceramic cooking surface. When during manufacturing or distribution a defect is detected in the cooktop, the defective cooktop is heated to a predetermined temperature to allow the silicone sealant to be easily removed without using a knife or other potentially damaging devices. Once the silicone sealant is removed, the glass-ceramic cooking surface and/or the cooktop frame may be reused in another cooktop assembly.


REFERENCES:
patent: 4047977 (1977-09-01), Yoshida et al.
patent: 4312571 (1982-01-01), Ganzhorn
patent: 6455819 (2002-09-01), Pohl et al.
patent: 6652665 (2003-11-01), Sachdev et al.
patent: 2002/0000239 (2002-01-01), Sachdev et al.
patent: 2002/0018885 (2002-02-01), Takahashi et al.
patent: 2003/0140918 (2003-07-01), Tapian et al.
patent: 2004/0074522 (2004-04-01), Cary et al.

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