Heating – Work chamber having heating means – Having means by which work is progressed or moved mechanically
Reexamination Certificate
2000-06-05
2001-06-19
Wilson, Gregory (Department: 3749)
Heating
Work chamber having heating means
Having means by which work is progressed or moved mechanically
C432S152000, C099S44300R, C099S44300R
Reexamination Certificate
active
06247922
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an oven, comprising a housing provided with heating means, as well as an endless conveyor belt on which products to be heated can be accommodated and can be transported through the housing between an entrance to and an exit from said housing, which conveyor belt is guided in the housing helically around each of two drums, which are arranged in the housing such that they can be driven about their vertical axis, and is guided straight between the two helical paths.
BACKGROUND OF THE INVENTION
An oven of this type is disclosed in EP-A 558 151. The conveyor belt thereof is held clamped around the two drums under the influence of a pretensioning force. The drums can drive the conveyor belt under the influence of the friction generated by this pretensioning force.
The conveyor belt is additionally subjected to the tensile force generated by the drums, which is required in order to propel the conveyor belt in the direction of transport. This tensile force can be appreciable since it must be greater than the frictional forces produced by the means supporting the transport.
The support for the conveyor belt comprises a number, usually two or three, of parallel guide sections over which the conveyor belt slides. At the location of the drums said frictional forces are directly cancelled out by the driving action of the drums, so that the tensile forces in the conveyor belt remain restricted at this location. However, especially in the belt return loop and in the section of the conveyor belt that crosses between the drums fairly high tensile forces arise.
The tensile forces arising in the belt return loop are partly compensated for by an axillary drive unit which is connected to a return shaft at the location of the entrance to the housing.
These problems, which are associated with the tensile force in the conveyor belt, arise to an increased extent in ovens of a larger capacity, that is to say ovens with a fairly broad conveyor belt. In particular the section of the conveyor belt that forms the crossover from the first to the second helical path is exposed to fairly high tensile forces.
SUMMARY OF THE INVENTION
The aim of the invention is to provide an oven of the abovementioned type with which the forces arising in the conveyor belt can be better controlled. Said aim is achieved in that the conveyor belt is supported, over at least one of the straight guided paths, by support means that can be moved in the same direction as the conveyor belt.
Compared with support by means of guide sections, the support means according to the invention first of all result in a lower frictional resistance. The tensile force in the belt decreases as a result, especially in the relatively highly stressed section of the conveyor belt close to the run-in into the second helical path.
A further reduction in the tensile force in the conveyor belt can be obtained if the support means exert a driving action on the conveyor belt in the direction of transport thereof. Said driving action can, for example, be obtained in that the support means can be driven at a speed which is higher than that of the conveyor belt.
Because the support means run somewhat faster than the conveyor belt, the latter is pulled along in the direction of transport as a consequence of the sliding movement and friction generated. The tensile force in the belt is further reduced as a result, especially at the location of the run-in into the second helical path.
The support means can have their own independent drive, which must be synchronised with the drive for the drums. Preferably, the support means can be driven by means of a drive which is coupled to at least one of the drums. The drive concerned can be a drive with chains, gears and the like. The advantage of this is that in this case no separate electronic control is required for driving the support means, whilst synchronous running is nevertheless obtained.
The support means can be constructed in various ways. According to a first possibility the support means are an endless element having an upper part on which the conveyor belt bears, which upper part can be moved in the same direction as the conveyor belt. Such an element can comprise, for example, a chain which is guided over two shafts which are provided with sprockets.
Such a chain can comprise links which, in the upper part, each have a support surface facing the conveyor belt. Preferably two or three parallel chains are used. Of course, an ordinary chain can also be used.
According to an alternative possibility, the endless element can comprise a flexible belt. According to a further alternative the support means can comprise at least one support roller or support shaft.
A wire belt known per se is used in the oven according to the invention, which belt comprises wire pieces which are oriented transversely to the conveyor belt and are attached to one another, such that they can rotate, around two axes oriented transversely to the direction of transport, one of which is in the plane of the conveyor belt and the other of which is oriented perpendicularly thereto, as well as at least one conveyor chain which is connected to or incorporated in the wire belt, which wire belt is guided over return shafts which are provided with sprockets for the conveyor chain.
At least one of the return shafts can be driven to provide supplementary driving of the conveyor belt in the direction of transport. Furthermore, with this arrangement a tensioning device is provided for tensioning the conveyor belt around the two drums.
The support means according to the invention can be arranged at various locations in the belt path as a whole. According to a first possibility, the support means are arranged below the straight path which extends between the two helical paths and is located inside the housing.
The support means can also have been arranged below the return path which extends between the exit from and the entrance to the housing.
REFERENCES:
patent: 3269142 (1966-08-01), DeMola et al.
patent: 4944162 (1990-07-01), Lang et al.
patent: 5243962 (1993-09-01), Hwang
patent: 5329916 (1994-07-01), Lygum
patent: 5836240 (1998-11-01), Kuenen
patent: 6065463 (2000-05-01), Martin
patent: 0558151A1 (1993-09-01), None
patent: 0578523A1 (1994-01-01), None
Koppens B.V.
Wilson Gregory
Young & Thompson
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