Plastic article or earthenware shaping or treating: apparatus – Distinct means to feed – support or manipulate preform stock... – Female mold type means
Patent
1996-02-01
1998-06-30
Wu, David W.
Plastic article or earthenware shaping or treating: apparatus
Distinct means to feed, support or manipulate preform stock...
Female mold type means
425127, B23B 300
Patent
active
057730369
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for extrusion-coating a tube, or the connection zone of a tubular composite body, which zone is to be sealed, with rubber or plastic (thermoplastic; thermoplastic elastomer), in particular for extrusion-coating a hose connection, comprising a connection pipe made of metal or plastic (e.g. polyamide), onto which the rubber or plastic hose section(s) is/are pushed.
2. The Prior Art
With respect to hose connections (e.g. molded hose branchings) using a connection pipe (e.g. a T-shaped piece of pipe), such hose connections being specified here as the main field of application, a comprehensive state of the art has developed heretofore, whereby reference is made, by way of example, to the following published references: 665; DE-C-40 25 141; DE-A-41 02 700; EP-A-0 243 216; EP-A-0 564 990.
In conventional mold separation for producing the above hose connections, the hose is, within the zone of the connection pipe, pressed onto the pipe with pretension, so that during the injection molding, the hose is not displaced by the injection pressure, and compression of the coating can be obtained at the same time. Normally, this is accomplished via reduction of the diameter of the tool enveloping the article; i.e., the smaller the diameter the greater the pressure applied to the area. From this results greatest possible compression and fixation during the injection and dwell process steps. However, if such pretensioning is applied to a degree such that such sealing is successful, this may under certain circumstances lead to damaging of the hose within the clamping zone of the mold separation. At the same time, differences in the thickness of the wall of the hose lead to even more damage if a thicker wall is obtained. With decrease in the thickness of the wall, the required compression of the coating is not assured, and such decrease leads to change in the position of the hose and to excessive injections, which make the parts unusable.
SUMMARY OF THE INVENTION
In order to counteract such drawbacks, a device is proposed in accordance with the invention which, in addition to the fixed molding tool contour with injection nozzles, has at least one, particularly at least two slide clamps, whereby the sealing surface of the latter substantially has the contour of the surface of the article directly opposing it within the sealing zone.
It is particularly advantageous if two to six slide clamps are present, whereby the numerical data specified relate to one circumferential unit of the tube to be coated all around, or of the connection zone of a tubular composite body, said zone having to be sealed. Example: If three hose sections are pushed onto a T-shaped piece of pipe, there are three sealing zones and, therefore, also three circumferential units with respect to the slide clamps. With, for example four slide clamps per circumferential unit, the total device consequently has (3.times.4=12) slide clamps.
Usefully, hydraulically controlled slides are used as slide clamps. Such slides assure a relatively uniform pressing of the area if the stroke of displacement of said slides is capable of significantly falling short of the pretension diameter of the sealing contour; i.e., the slides run up on the sealing surface with a preselected hydraulic pressure and come to a standstill only after a desired area pressing (counterpressure) has been reached.
The slides exceed or fall short of the diameters in the sealing zone depending on the wall thickness of the hoses. In this way, a "hydro-rubber-elastic" pretension is obtained which, in addition, permits further variations of the area pressing through the preselected control pressure. At the same time, owing to such "hydro-rubber-elastic" pretension, damage of the hoses within the clamping zone is avoided, as are the frequently present fabric inserts, namely with greatest possible reproducibility of the injection and dwell parameters during the coating process. In addition, the pre-mounted position of
REFERENCES:
patent: 4676532 (1987-06-01), Gronau et al.
patent: 5356587 (1994-10-01), Mitsui
Ahlers Michael
Stuhrmann Dirk
Zimmer Detlef
Phoenix Aktiengesellschaft
Wu David W.
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