Patent Publication Number: US-6665950-B1

Title: Gas-heated infrared radiator for an infrared drying unit

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the US national phase of PCT application PCT/EP00/05447 filed Jun. 14, 2000 with a claim to the priority of German patent application 19928096.7 itself filed Jun. 19 1999. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an infrared radiator for an infrared drying unit with a radiator housing that is subdivided internally by a gas-pervious burner plate into a distributing compartment for the gas/air mixture and into a combustion compartment. A large portion of the energy contained in the combustion gases is convectively transmitted in the combustion compartment to a solid body that gives this energy up as infrared radiation at its front side. The radiator has a back housing wall mounted on a mixing tube through which an gas/air mixture is supplied to the distributing compartment, the mixing tube having on its end remote from the radiator housing a gas nozzle with a gas feed, being connected to an air feed, and being fixed on a frame of the drying unit. 
     BACKGROUND OF THE INVENTION 
     Such infrared radiators are as is known installed in dryer systems that serve for drying web-like materials, for example paper or cardboard webs. Depending on the width of the web to be dried and the desired heat capacity, the necessary number of radiators are assembled in one or more rows to a drying unit, the individual radiators being mounted immediately adjacent one another. Such an infrared radiator is described in EP 0,128,202. 
     Gas-heated infrared radiators are subject to wear in use so that it is necessary to replace them after a service life of about two to four years. In addition they must be serviced as a rule once or twice a year in order to check whether the gas nozzle in the mixing tube or the radiator itself is dirty. Switching and servicing the known radiators is very time intensive since several steps must be carried out to remove the radiator housing and clean the nozzles, carried out when the dryer is cooled off and is thus not in use. This creates down times for the equipment in which the drying unit is integrated, for example a coating system for paper or cardboard webs. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the invention to improve on this type of infrared radiator and/or mount therefor so that it can be removed as quickly as possible from and reinstalled back into an infrared drying unit. 
     SUMMARY OF THE INVENTION 
     This object is attained according to the invention in that the radiator housing is connected on its rear side with the frame via releasable fastening means which are manually releasable from the front side. 
     The radiator can thus be rapidly removed and again reinstalled, working from the easily accessible front side. Servicing parts of the radiator can be done outside the equipment under no particular time constraints. 
     In one embodiment, the radiator housing is bolted on the mixing tube via screws that can be tightened or loosened from the radiating front side of the radiator. Preferably the screws are so constructed and screwed in so far that their heads are in the cooler distributing compartment for the gas/air mixture behind the burner plate and not in the hot combustion compartment in front of the burner plate. The burner plate thus has corresponding bores through which the screw heads can be reached with a tool. If a metal mesh overlies the radiating surface, it is either only clipped in place so it is easily removed or it also has aligned bores. 
     The radiator is particularly advantageous and easy to remove when equipped with a speed coupling that is releasable by pushing or pulling on the front side, that is by a force parallel to the axis of the mixing tube. The speed coupling can be made of a standard coupling mechanism and includes as coupling parts a sleeve-shaped holding part and an insert part that can be coupled with each other, the coupling force being exerted by spring elements that free the insert part when pushed or pulled. 
     The speed coupling is between the housing back wall and the mixing tube, between the gas-supply line and the gas nozzle, or inside the mixing tube. The gas nozzle is preferably fixed in the mixing tube. In the particularly advantageous embodiment, the gas nozzle is removable from the drying unit with the mixing tube and the radiator housing fixed thereto and can thus be serviced outside the equipment. When the gas nozzle is bolted into one coupling part of the speed coupling, it is accessible after opening of the speed coupling and can simply be screwed out. 
     A preferred and even particularly advantageous embodiments of an infrared radiator is secured in a solid and gas-tight manner on the frame and that is removable by pressure on the front side of the radiator housing. 
     The infrared radiator has a socket part, an insert part at least partially slidable against the force of a spring into the socket part, and a latching mechanism with a latch element and a complementary socket element. The latching element is fixed on one of the coupling parts, moves on fitting of the one coupling part into the socket element on the other coupling part, and is mounted on a pivotal mechanism that is actuated on movement of the insert part of the speed coupling against the socket part and alternately moves the latch element into a latch position holding the coupling parts together or an unlatched position in which the coupling parts can be separated from each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The drawing shows preferred embodiments of the invention. Therein: 
     FIG. 1 shows an embodiment of an infrared radiator with a mixing tube bolted to the radiator housing; 
     FIG. 2 shows the radiator housing of another embodiment of a radiator when unbolted; 
     FIG. 3 shows a section through an infrared radiator with a speed coupling; 
     FIG. 4 is a section through the end of a gas-feed tube with the socket part of the speed coupling; 
     FIG. 5 is a side view of the elements of FIG. 4; 
     FIG. 6 is a section through the mixing tube with the insert part of the speed coupling; and 
     FIG. 7 is a side view of the elements of FIG.  6 . 
    
    
     SPECIFIC DESCRIPTION 
     The infrared radiator includes a radiator housing  1  that is formed by perpendicular side walls  2  and a back wall  3 . 
     The interior of the radiator housing  1  is subdivided by a gas-pervious burner plate  5  whose back face forms with the back wall  3  a distributing compartment for the supplied gas/air mixture. Downstream in the flow direction from the burner plate  5  is a combustion compartment  7  in which the gas/air mixture flowing through holes  8  in the burner plate  5  is burnt. A large portion of the combustion energy is transmitted convectively to solid bodies that give it up as infrared radiation on the front side of the radiator. 
     In the embodiments according to FIGS. 1 and 3 the solid bodies are a ceramic burner plate  5  and a mesh  23  with a frame  4 . In the embodiment according to FIG. 2 the solid bodies are several radiator bodies  24  and a mesh  23  that holds the radiating bodies  24 . In all embodiments the mesh  23  forms the front side of the radiator. 
     The radiator housing  1  is carried by a mixing tube  9  fixed to its back side and opening into the distributing compartment  6 . In order to distribute the gas/air mixture uniformly over the back face of the burner plate  5 , a baffle  10  is provided in the distributing compartment  6  against which the mixture flowing out of the mixing tube  9  impinges. 
     A gas nozzle  1  connected to a gas-supply line  12  is screwed into the upper end of the mixing tube  9  turned away from the radiator housing  1 . The gas-supply line  12  is connected with a manifold  13  from which a plurality of radiators are supplied with gas  14 . Air  15  is supplied via a hollow transverse beam  16  on which the mixing tube  9  is mounted. The connecting conduit  17  for the air supply opens into an upper part of the mixing tube  9  in a downwardly open air compartment  18  surrounding the outlet end of the gas nozzle  11 , so that a mixing compartment  19  of the mixing tube  9  is filled from the top with a gas/air mixture. 
     Several radiators are arranged directly over the width of the web to be dried and form a drying unit. If the desired heat capacity requires it, several rows can be arranged one behind the other in the web-travel direction. The radiators are fixed on a holder frame of the drying unit. In the embodiments according to FIGS. 1 and 3 the hollow transverse beam  16 , on which the mixing tube  9  is mounted with the housing  1 , serves to hold the radiator. The hollow transverse beam  16  is thus part of the frame of the drying unit. 
     It is significant for the invention that the radiator housing  1  be secured with the frame (in FIGS.  1  and with the hollow transverse beam  16 ) by releasable fastening means that is manually releasable from the radiating front face. 
     In the embodiment according to FIGS. 1 and 2, the radiator housing is releasably secured by its back wall  3  at the end of the mixing tube  9  via screws  20 . To this end the back wall  3  has an annular flange  21  that is solidly bolted to a flange-shaped widened end of the mixing tube  9 . The screws  20  are so short that their Allen heads are in the mounted position of FIG. 1 inside the distributor compartment  3 , that is behind the burner plate  5 . When the radiator is in use they are thus in a completely flame-free portion of the radiator and are not excessively heated. Since the screws  20  have to be loosened from the front side of the radiator, the burner plate  5  and the radiator body  4  have aligned bores  22  through which a tool can be passed to loosen and tighten the screws  20 . 
     According to further embodiments of the invention the releasable fastening means is a speed coupling that is released by pressure or tension from the front side, that is by a force aligned axially with the mixing tube  9 . The speed coupling is based on a standard coupling mechanism and is comprised as is known of a sleeve-like socket and an insert that can be clamped together when axially fitted together and that can also be released from each other by an axial pull or push. The coupling force is applied by springs that are released by pushing or pulling on the insert. Preferably the coupling parts are tubular so that the gas, the air, and/or the gas/air mixture can flow through the speed coupling. 
     It is important for the invention that the force for connecting or releasing be exerted exclusively from the front side of the radiator housing without having to move the radiator housing  1  to the side. 
     According to an embodiment, the speed coupling is mounted between the housing back wall and the mixing tube. The mixing tube thus stays when released with the frame; only the radiator housing is released. 
     According to the preferred embodiment, the speed coupling is mounted on the upper end of the mixing tube between the gas-supply line and the gas nozzle. The releasable part of the speed coupling holds the gas nozzle. Thus the radiator with the mixing tube and the gas nozzle mounted on it are released. The gas-supply is fixed to the frame. The elements for feeding in gas are made sufficiently robust that they serve in use as holder for the radiator with the mixing tube. A preferred embodiment of such a infrared radiator is shown in FIGS. 3 through 7 and is described in detail below: 
     The speed coupling includes two coupling parts: a socket with the gas supply (FIGS. 4 and 5) that is mounted on the hollow transverse beam  16  and an insert (FIGS. 6 and 7) that is formed by the upper end of the mixing tube  9 . 
     The socket part has a sleeve-shaped housing  24  that is bolted to the hollow transverse beam  16  as part of the frame. The housing  24  has in its lower portion a somewhat restricted inside diameter so as to form an annular restriction at the transition between the lower part and an upper part. The housing  24  is closed at the gas-supply side with a plug  26  that has a central passage to which is connected the gas-supply line  12 . Inside the housing  24  the passage holds a central tube  26  over which is fitted a compression spring  27 . The spring  27  presses against a seal member  28  that fits the inside diameter of the housing  24  and has a central throughgoing passage  29  in which the end of the tube  26  fits gas-tight. The seal member  28  slides on the tube  26  axially, its upper end position being determined by the plug  25  and its lower end position by the restriction inside the housing  24 . The gas can thus travel from the supply line  12  through the tube  26  and the seal member  28  into the lower open part of the housing  24  where there is a lateral opening  30  for the air supply  17 . 
     The insert part of the speed coupling is formed by the upper end of the mixing tube  9  that is closed by the gas nozzle  11 . The outside diameter of the end of the mixing tube  9  with the gas nozzle  11  is dimensioned for insertion into the inside diameter of the lower end of the housing  24 . On insertion of the mixing tube  9  with the gas nozzle  11  into the housing  24  the upper end of the gas nozzle  11  engages sealingly on the seal member  28  which covers the nozzle opening with the throughgoing passage  29  so that gas can flow out of the gas-supply line  12 . The insert part of the speed coupling (the end of the mixing tube  9  with the gas nozzle  11 ) is thus slid against the force of the spring  27  into the housing so that, as shown in FIG. 3, the gas nozzle  11  is wholly and the mixing compartment  19  partially in the housing  24 . In this position the lateral opening  31  is aligned with the opening  30  in the housing, to which the air supply  17  is connected. Air can thus flow through both openings  30  and  31  into the air compartment  18 . 
     In order that the insert part of the speed coupling is connected both without leakage and solidly on the mixing tube, while still being removable from the socket part formed by the housing  24 , both parts carry respective elements of a latching mechanism that is released by pressure on the front side of the radiator housing  1 . The latching mechanism includes a latching element fixed on one part of the speed coupling and a complementary seat that is fixed on the other part of the speed coupling. When the two speed-coupling parts are fitted together the latch element fits into the seat element and latches there. To this end it is mounted on a pivotal mechanism that is actuated on movement of the insert part against the socket part. The pivotal mechanism rotates the latch element on each movement of the insert part against the socket part either into a latched position holding the coupling parts together or into an unlatched position in which the coupling parts are released from each other. 
     In the preferred embodiment according to FIGS. 3 through 7 the latch element is mounted outside on one side of the mixing tube  9 . It is formed of a latch pin  33  that is fixed to extend perpendicular through an end of a shaft  34  that is mounted on a lateral projection  32  so it can turn about an axis parallel to the longitudinal axis of the mixing tube  9 . The shaft  34  rotatably carries a cam  35  that pivots with the pin  33  fixed to it through 90° on each axial movement of the shaft  34 . The correspond socket element of the latch mechanism is mounted on the housing  24  of the socket part of the speed coupling. It is formed of a socket sleeve  36  fixed to the housing and in which the latch pin  33  fits when the coupling parts are moved together. The socket sleeve  36  has a latch in which the end of the shaft  34  with the latch pin fits like a key. On movement into the socket sleeve  36  the rotary cam  35  is held on the edge of the socket sleeve  36 . On moving into the socket sleeve  36  the cam is held on the edge of the socket sleeve  36 . Further axial shifting of the cam  35  rotates the shaft  34  with the latch pin through 90° so that the latch pin  33  moves into its latched position as shown in FIG.  1 . It is held in this position by the force of the compression spring  27 . 
     The speed coupling can be released by pressing against the front side of the radiator housing  1 . This moves the insert part with the gas nozzle  11  against the force of the spring  27  again into the housing  24 . The rotary cam  35  is rotated with the latch pin  33  through 90° into its unlatched position in the lock of the socket sleeve  36 . The insert part of the speed coupling can be pulled out so as to free the mixing tube  9  with the radiator housing  1  fixed to it. 
     According to a further embodiment not shown in the drawing the speed coupling is inside a two-part mixing tube, the nonremovable part of the speed coupling including the gas nozzle. This part with the gas nozzle thus remains on the frame after freeing of the radiator so the nozzle is freely accessible for servicing. 
     With the two last-described embodiments the gas nozzle preferably is bolted into a coupling part of the speed coupling. It is thus accessible after opening of the speed coupling and can be simply screwed out.