Apparatus for heating a sheet- or web-like material

Claim 2

Apparatus for heating a sheet- or web-like material during its transport through a processing machine, comprising at least one infrared heating panel facing the path of transport of the material and connected to an ac-source through a semiconductor switching means, a controlling circuit for delivering ignition impulses to the semiconductor switching means, wherein the ignition time within each half period of the supply voltage is determined by a control signal provided by a control means to the controlling circuit, which can be switched on and off by a monitoring circuit coupled to a detector means reacting to the transport speed, wherein said monitoring circuit comprises two or more zone detector means reacting to the presence of the material within a given zone extending transversely to the transport direction of the material on either side of the desired path of transport, and an AND-input circuit and/or an OR-input circuit, said input circuits controlling a switching means through a time-delay means for switching the controlling circuit on and off, wherein the controlling circuit is switched off if the material leaves said zone.

Claim 3

Apparatus according to claim 1, wherein the time-delay of said time-delay means is adjustable.

Claim 4

Apparatus according to claim 1, wherein the monitoring circuit will switch off the heating panel if the rate of passage of the web-like material through the processing machine becomes less than a reference rate and before it comes to a stop.

Claim 5

Apparatus according to claim 3, wherein the monitoring circuit includes a first time-delay means which switches on the controlling circuit when a given length of time has lapsed since the transport speed has exceeded the reference rate.

Claim 6

Apparatus according to claim 3 or 4 wherein the monitoring circuit includes an adjusting device for adjusting the reference rate at which the controlling circuit is switched off.

Claim 7

Apparatus for processing sheet-like material during its transport through a processing machine, comprising at least one infrared heating panel facing the path of transport of the material and connected to an ac-source through a semiconductor switching means, a controlling circuit for delivering ignition impulses to the semiconductor switching means, wherein the ignition time within each half period of the supply voltage is determined by a control signal provided by a control means to the controlling circuit, wherein said controlling circuit can be switched off by a monitoring circuit coupled to a detector means, said detector means being mounted, seen in the transport direction, just before the heating panel and provides a binary signal having the first binary value at the presence of a material sheet opposite the detector means and having the second binary value at the absence of a material sheet opposite the detector means, wherein the monitoring circuit, in response to said binary signal, switches on the controlling circuit at the presence of a material sheet and switches off the controlling circuit if within a first predetermined period after the passage of a material sheet no subsequent sheet is detected by said detector means, wherein the monitoring circuit also switches off the controlling circuit if a material sheet remains longer than a second predetermined period opposite the detector means.

Claim 8

Apparatus for processing sheet-like material during its transport through a processing machine, comprising at least one infrared heating panel facing the path of transport of the material and connected to an ac-source through a semiconductor switching means, a controlling circuit for delivering ignition impulses to the semiconductor switching means, wherein the ignition time within each half period of the supply voltage is determined by a control signal provided by a control means to the controlling circuit, wherein said controlling circuit can be switched off by a monitoring circuit coupled to a detector means, said detector means being mounted, seen in the transport direction, just before the heating panel and provides a binary signal having the first binary value at the presence of a material sheet opposite the detector means and having the second binary value at the absence of a material sheet opposite the detector means, wherein the monitoring circuit, in response to said binary signal, switches on the controlling circuit at the presence of a material sheet and switches off the controlling circuit if within a first predetermined period after the passage of a material sheet no subsequent sheet is detected by said detector means, wherein the monitoring circuit also switches off the controlling circuit if a material sheet remains longer than a second predetermined period opposite the detector means.

Claim 9

Apparatus according to claim 6, wherein both said periods are adjustable.