The present invention refers to a method for continuous in line production of damper elements, comprising in cross section two substantially in parallel with a certain relative slit width arranged sheets, which slit is bridged at the sheet edges by cantlists, in such a way that the sheets and the cantlists delimit at least one space inside the element, which space is filled with a foamed material. Such damper elements are for example known from DE-A-1914536.
The element in accordance with above is reminiscent of elements that can be part of e.g. folding doors, at which it generally meets the necessary demands regarding rigidity and insulation.
Adjustable damper blades for use as control device, fire damper, baffle and the like in ventilation constructions can have a length of up to 2 metres. These elements are rotatable between different adjustment positions and exposed to considerable torsion stresses, and do therefore need higher torsion rigidity. If necessary torsion rigidity is not obtained, the damper blade adjustment function will not be satisfactory, which may bring on serious consequences if the blades form part of a fire damper. For this purpose, it has usually been necessary to assemble a damper blade by means of screws, blind rivets, spot welds or other means which have made production of such damper blades relatively work intensive. The demands on close tolerances, e.g. absence of play, do also make production more expensive.
The purpose of the present invention is to provide a damper blade, by which high torsion rigidity is obtained without use of expensive screws, blind rivets or spot welds for assembly.
For this purpose the invention is characterized in that sheet plate is pulled in parallel off two magazine rolls and said sheets are formed in parallel by folding into a top sheet and a bottom sheet, the two folded sheets are joined continuously by means of the elastic sections of the cantlists cooperatively with folded sections at the edges of the sheets to achieve mechanical joining of the element before foaming, the foam is injected in the space between the sheets and the cantlists by means of a nozzle which reaches in between the sheets, the foam is activated for expansion and setting, and the composite structure is cut into suitable lengths by means of a flying chopper.
The invention will be described hereinafter with reference to embodiments shown in the enclosed drawings, wherein
The damper blade, shown in the drawings, comprises an external shell consisting of two metal sheets 10 being profiled by folding, which are joined by means of cantlists 11 along both longer sides.
Quadrangular axle spindles 12 of metal are placed between the sheets 10 at both short ends of the damper blade. For fixing of the axle spindles 12 in the longitudinal direction of the blade, the sheets are provided with grooves 13, which connect to the quadrangular form of the axle spindles. In addition, an U-shaped mountings 14 is pressed onto each short end of the blade, thus tightening the sheets against the axle spindles. The mountings 14 in its turn, are attached to the sheets 10 in a very effective and simple way, by a prick punch on each side, using the axle spindles as a dolly for the prick punches.
The axle spindles 12 normally extend only about 50 mm into the damper blade from each short end. The torque that may arise between both mounting ends of the axle spindles, are transmitted very effectively and without play to the sheets of the damper blade by said mounting.
The sheets 10, cantlists 11 and mountings 14 enclose a space filled with a foamed material 16, e. g. a polyurethane foam. This foam material adheres to the insides of the sheets, and contributes actively to make the damper blade torsion resistant.
The sheets 10 are provided with hook-shaped folded sections 17 at the side edges, which sections are facing the interior of the blade. The cantlists 11 present elastical sections, which cooperate during assembling of the element, with the folded sections 17, producing mechanical joining of the element before foaming of the foam material.
The elastical sections comprise a centrally situated web section 18, which extends in between the hook-shaped folded sections 17 of the sheets 10, and is coaxial with the central plane of the element. The web section 18 turns into a shoulder section 19 with hooking means 20, which grasp the hook-shaped creased section 17 of the sheets 10.
The above described attachment of the sheets via the cantlists, provides a sufficient strength for holding the parts together during entry and expanding of the foam. This makes it possible to produce the damper blade from thin sheet metal, e.g. 0,5 mm galvanized sheet metal. In this respect, the blade can be continuously produced in a line, wherein continuous sheets are fed in parallel from two magazine rolls, and formed parallelly into one top sheet and one bottom sheet by means of roll folding. Both folded sheets are thereafter continuously assembled by means of the cantlists 11. Foam is then injected in the space between the sheets and the cantlists via a long nozzle, which reaches between the sheets before they are assembled by the lists. The foam is activated, expands and sets to its final shape by passage trough an oven.
Now the foam forms a locking for the hooking means of the cantlists, so that these can not slip away from their grip on the hook-shaped folded sections 17 of the sheets 10, even if the composite element is exposed to considerable strains.
Crosscutting into adequate length is thereafter repeatedly executed in a so called "flying chopper". Finally, the axle spindles are mounted in the intended positions, by inserting into the grooves 13, and the mountings 14 are mounted in the previously described way.
The invention is not limited to the above described embodiment, instead more variants are conceivable within the scope of following claims. For instance, the sheets 10 can be folded otherwise than shown, wherein the sections 17 do not need to be hook-shaped.