LOW COST/IMPEDANCE PROTECTED FUSING SYSTEM
Original Publication Date: 1986-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
Figure 1 illustrates a fuser system for electrostatographic reproducing apparatus which includes a pressure roll 10 and a fuser roll 12 forming a fusing nip therebetween. The fuser roll comprises a cylindrical ceramic member 14 with electrical contacts as mounting blocks 16 at both ends connected to a power source 18. Alternatively, of course, the fuser roll could be a solid ceramic rod. The ceramic material is one having a positive temperature coefficient in that it provides increasing resistance with an increase in temperature. Furthermore, positive temperature coefficient ceramic materials can be formulated to exhibit a sharp increase in resistance at a predetermined switch point (T,) as shown in Figure 2. Such material provides an economical method of temperature control by combining the function of the heater and thermostat in this ceramic element by utilizing the steep positive temperature coefficient characteristics as illustrated in Figure 2. As the temperature of the element rises, the resistance of the ceramic increases thus reducing the input power to the circuit and maintaining a relatively constant temperature. The illustrated system provides a low cost, reliable, simplified fuser system with automatic current limiting safety features and the elimination of several devices such as resistance heating elements, thermostats, fusible temperature links, temperature sensing transducers and electronic control systems.