Method and apparatus for uniformly drying moving webs

A drying system comprising:

• means for moving a web along a path extending through a drying station;
• said drying station comprising a plurality of elongated drying means each extending transverse to the path of movement of said web;
• said drying means being arranged at spaced intervals along the path of said moving web;
• each of said drying means comprising side-by-side dryer sections each arranged to be heated by a flame sustained by an air/gas mixture;
• a gas supply;
• a first combustion air supply;
• an air/gas mixing chamber for each dryer section for communicating with said air supply and said gas supply for mixing air and gas entering said mixing chamber and delivering the air/gas mixture to the heating means of each dryer section;
• means for igniting said air/gas mixture to heat each of said drying sections;
• regulating means for selectively controlling the air/gas mixture entering said mixing chamber whereby the heat intensity of said drying sections are regulated between a high and a low intensity level to selectively control the amount of drying experienced across said moving web by each drying means whereby maximum drying for each longitudinal web section is obtained when the drying sections of all of said drying means associated with said longitudinal section of the web are controlled to provide high intensity heating and for incrementally reducing the total amount of drying for each longitudinal section by selectively operating the control means associated with each drying section.

Apparatus for regulating an air/gas mixture delivered to a combustion chamber comprising:

• a plurality of conduits each having an inlet coupled to the manifold for receiving an air/gas mixture and an outlet;
• each of said conduits delivering an air/gas mixture entering its associated inlet to its associated outlet;
• said outlets communicating with said ignition chamber;
• a control inlet in each of said conduits being arranged intermediate the inlet and outlet of said conduits and communicating with the interior of said conduits;
• a source of air under pressure;
• delivery means for delivering said source to each of said control inlets;
• said delivery means including regulating means for regulating the flow level of air from said source to each of said control inlets whereby the intensity of the flame produced by the air/gas mixture in the ignition chamber is inversely proportional to the flow level delivered to said control inlet from said source.

A method for retaining the moisture profile across a moving paper web within a desired range comprising the steps of:

• moving the web past a dryer unit comprised of dryer sections arranged side-by-side and spanning across the width of the web;
• each section having a mixing chamber for delivering an air/gas mixture to the heating elements thereof, each mixing chamber having a mixture controller;
• measuring the moisture content across the web to provide a moisture profile;
• selectively operating the mixture controller to increase the output energy of only those drying sections associated with the longitudinal sections of the web whose moisture profile is above a predetermined level.

Apparatus for regulating an air/gas mixture delivered to a combustion chamber comprising:

• a conduit having a first inlet for receiving an air/gas mixture and an outlet, said conduit delivering the air/gas mixture entering said inlet to said outlet;
• said outlet communicating with said combustion chamber;
• a mixing device having a first inlet for receiving gas, a second inlet for receiving air and a mixing region for mixing said air and gas and delivering the mixture to the conduit inlet;
• a control member slidably mounted within said mixing device and means for regulating the position of said control member in one of said openings of said mixing device whereby the proportionate amounts of gas and air reaching said mixing region first inlet is determined by the position of said control member.

Apparatus for improving the uniformity and percent of moisture content across a web undergoing drying comprising:

• a plurality of elongated dryer units arranged transverse to the direction of movement of the web and each comprised of a plurality of dryer sections, each dryer section arranged to dry a particular section of the web;
• each dryer section comprising a radiant energy emitter and means for receiving an air/gas mixture for heating the emitter when ignited, the proportion of which mixture controls the radiant energy output level of the associated dryer section;
• regulating means for selectively regulating the air/gas mixture for each dryer section between predetermined upper and lower energy levels, said lower energy level being at least sufficient to sustain combustion of the air/gas mixture;
• means for individually operating said regulating means to control drying across each of said dryer units to provide localized drying at a selected one of said upper and lower energy levels of any desired longitudinal section of the moving web, the amount of localized drying being the cumulative sum of the individual dryer sections of said dryer units for drying a section of the web to thereby achieve a more uniform moisture distribution across the web.

Apparatus for regulating an air/gas mixture delivered to a combustion chamber comprising:

• a conduit having a first inlet for receiving an air/gas mixture and an outlet, said conduit delivering the air/gas mixture entering said inlet to said outlet;
• said outlet communicating with said combustion chamber;
• a mixing device having a first inlet for receiving gas, a second inlet for receiving air and a mixing region for mixing said air and gas and delivering the mixture to the conduit inlet;
• a control member movably mounted within said conduit and means for moving said control member to a first position to provide a large opening for passage of gas therethrough and to a second position to provide a restricted opening for passage of gas therethrough.