Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-06-30
2001-08-28
Ball, Michael W. (Department: 3752)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S244130, C156S244270, C156S253000, C156S294000, C156S322000, C156S500000, C156S552000
Reexamination Certificate
active
06280554
ABSTRACT:
The present invention relates to the manufacture of drip irrigation conduits.
A manufacturing method for such a conduit is already disclosed in European Patent Application No. 98106765 and is of the type consisting in:
manufacturing dripper units,
introducing said dripper units one after the other inside said conduit while the latter is being formed in an extruder, then calibrated in a calibrator, and
heat welding said dripper units to the inner wall of the conduit during its progression downstream from said extruder then cooling said conduit and perforating the latter opposite each dripper unit to make it communicate with the exterior.
According to this known method, the dripper units are introduced into the conduit being formed using a thread onto which the dripper units are secured at a regular distance from each other, the distance between them determining that at which they will be fixed to the inside of the conduit. The traction force on the succession of dripper units results from that exerted by the last dripper unit which has just been heat welded to the inner wall of the conduit. This means that, before passing through the centre of the extruder the dripper units move forwards at the speed of the conduit in formation, otherwise the thread is liable to break. This results in a complication for the installation, since means must be provided not only for manipulating the thread, but also for preventing the breakage thereof.
Moreover, according to the principle of this device, the dripper unit which has just been welded to the inner wall of the conduit pulls, via the thread, the following dripper units and allows them to move forward. Tests have shown that the forces set in play for the traction of the following dripper units systematically lead to more or less significant tearing of the back of the dripper unit which has just been welded, which makes the conduit unusable.
Another drawback of this method consists in that it does not allow satisfactory preheating of the face of the dripper units intended to come into contact with the inner wall of the conduit to facilitate the welding thereof to the latter, given the high speed at which the dripper units attached to the thread move forward prior to welding. This leads on the one hand to a more complex design of the dripper units (smaller contact surface with the conduit) and on the other hand, to using adhesive materials or materials with a lower softening point which are ill suited to the injection moulding technique, which makes the manufacture of the dripper units difficult and expensive.
The object of the invention is to overcome these drawbacks.
The invention thus concerns a manufacturing method of the type indicated hereinbefore which is characterised in that:
said heat welding step is executed downstream of said calibrator by pinching the dripper unit and the wall of said conduit between first and second opposing surfaces, one of which is driven at the speed of progression of the conduit and the other is arranged on a fixed support member forming a feed guide for the dripper units.
As a result of these features, the dripper units are fed individually by the guide forming a support surface and acquire the speed of the conduit only during the short moment when they undergo pinching against the inner wall of the conduit and while they are heat welded to the inner wall. Consequently, the manufacturing line can be considerably simpler. It will also be noted that the distance between the dripper units in the finished conduit is obtained without other means or any additional steps.
According to a preferred embodiment, the dripper units are presented for the pinching step one after the other contiguously by their ends.
It is thus possible to cause the dripper units to advance at the desired speed and to vary the pitch at which the dripper units are fixed in the conduit at will by increasing or decreasing the feed speed of the dripper units into the pinching station.
According to an advantageous embodiment, the method of the invention further includes an additional step consisting in preheating the face of the dripper units intended to be turned towards the inner wall of the conduit before the latter are pinched between the inner wall of the conduit and the first and second opposing walls.
This facilitates, in particular, the welding of the dripper unit to the conduit, which cannot in certain cases (small thickness of its wall), provide the quantity of heat necessary to the dripper unit to achieve high quality welding.
The invention also concerns a manufacturing line for the implementation of the method according to the invention, including a dripper unit feed station, followed by a station for the extrusion and calibration of said conduit and a conduit cooling station, said line being characterised in that downstream of said extrusion and calibration station a pinching station for pressing each dripper unit against the inner face of said conduit during a heat welding operation is provided, and in that a guide for the dripper units links said feed station to said pinching station passing through said extrusion and calibration station, said guide defining a support surface for said dripper units in said pinching station.
The invention also concerns a conduit obtained via the method of the invention, characterised in that it includes dripper units whose face turned towards said conduit is flat and in that opposite each dripper unit, said conduit has, in cross-section, a section which is flattened on the side on which each dripper unit is situated.
Complementary features of the method, the manufacturing line and the conduit according to the invention are defined in the dependent claims.
REFERENCES:
patent: 3619316 (1971-11-01), Ishida
patent: 5271786 (1993-12-01), Gorney et al.
patent: 5282916 (1994-02-01), Bloom
patent: 5324371 (1994-06-01), Mehoudar
patent: 5324379 (1994-06-01), Eckstein
patent: 5676897 (1997-10-01), Dermitzakis
patent: 5711214 (1998-01-01), Lauderbaugh et al.
patent: 5744779 (1998-04-01), Buluschek
patent: 5862652 (1999-01-01), Schoeler
patent: 5902047 (1999-05-01), Yeager
patent: 6039270 (2000-03-01), Dermitzakis
patent: 0 715 926 A1 (1996-06-01), None
patent: 0 872 172 A1 (1998-10-01), None
Buluschek Bruno
Lambert Gilles
Ball Michael W.
Griffin & Szipl, P.C.
Musser Barbara J.
Swisscab S.A.
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