Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Patent
1994-11-23
1996-05-14
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
723425, 72369, 264339, 425162, 425384, 425392, B29C 5308, B29C 5384
Patent
active
055164790
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method and a device for bending plastic pipes in which a plastic pipe or tube is heated at the bending point.
It is known to heat plastic pipes in a manner by placing the pipes into an oil bath of about 160.degree. C. and then manually bending the pipe around a bending mandrel or a bending roller into the desired shape. This known method is performed manually and in terms of the craftsmanship required is relativly complicated. Generally the method may be performed only by skilled workers. In addition, the exactness of the desired shape of the bent pipe is not reached in each case.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a method which is suitable to exactly and quickly converting the pipe into the desired shape, even when the method is performed by unskilled and unpractised workers.
According to the invention this is achieved by a method of the described art, wherein the pipe section is first heated in a water bath at about 80.degree. C. and then laid around one or more bending plates, depending on the desired shape, whereupon the bending plates are subjected to a heat source, for example a hot air blower, and partially heated, depending on the pipe material used, to a maximum of 160.degree. C. for 10 to 15 seconds, whereafter the pipe section is subjected to a first cooling process from inside the pipe using cold compressed air for 10 to 15 seconds, and where the pipe section is then placed in a cold water bath.
By using this method it is possible to very quickly and exactly convert pipe sections into a shape in one or more planes, whereby the production of these bent pipe sections is rapidly accelerated and reduced in cost.
The invention also includes a device in which a plurality of bending plates having flutes are positioned on a frame, depending on the desired shape, and an air heater, for example a hot air blower, is positioned opposite to each bending plate, displacable toward and away from the bending plate, and containing an air channel surrounding the bending plate, plus switch elements and control elements for controlling the process, especially for moving and switching the air heaters on and off and for introducing the cold compressed air to cool the bent pipe sections. Using the device according to the invention it is possible in a simple manner to lay the pipe sections, which are heated prior to bending in a water bath at 80.degree. C., and have a certain reset resilience, around the specially positioned bending plates and to move the air heaters toward the bending plates at the bending points.
A preferred embodiment of the device for implementing the method of this invention shows that the bending plates, having flutes defined therein according to the diameter of the pipe sections, are provided with at least one row of openings on each of their two surfaces for the cross flow of the hot air of the air heaters over the pipe section.
A further embodiment of the invention provides holes at the base of the flutes of the bending plates, which run into an exhaust conduit for the hot air provided in the bending plate.
A further embodiment of the invention shows that the bending plates contain two parts, in which an upper part has the shape of a semicircle only and is placed pivotably on a lower part, to make it possible to lay the pipe section into the bending plate.
The air heater apparatus may also have a hot air blower and an air channel for the hot air, the air channel having a cutout in a semicircular shape.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the method and the device according to the invention are illustrated in connection with the drawings, which show in:
FIG. 1 a schematic view of a pipe bending device,
FIG. 2 a top plan view of the device of FIG. 1,
FIG. 3 the part of the device of FIG. 1 containing the bending plates and the air heaters in enlarged scale,
FIG. 4 a top view on a bending plate, and
FIG. 5 a vertical cross section through the device along the section lines shown in FIG. 4.
DETAILED DESC
REFERENCES:
patent: 2571416 (1951-10-01), Brown
patent: 3184796 (1965-05-01), Southcott et al.
patent: 3965715 (1976-06-01), Parmann
Lippenoo Olaf
Schimmelpfennig Rainer
Aeroquip Zweigniederlassung der Trinoza GmbH
Tentoni Leo B.
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