Static molds – Core – Of plural sections
Patent
1985-12-04
1988-01-26
Crosby, Gene P.
Static molds
Core
Of plural sections
164346, 249 63, 249144, 425577, B22C 910, B29C 3348
Patent
active
047212802
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an injection moulding core for pipe bends which have at least one straight pipe terminal portion.
It is a known fact that the main problem in the manufacture of pipe bends with straight terminal pipes or with a tight sleeve using the injection mould process is presented by the mould core and that, using the core slide technique, the complete circular section along the whole length of the bend, of 90.degree. for example, can only be achieved if the condition R.ltoreq.2/3 D has been satisfied, whereby R is the bend mean radius and D is the internal diameter of the pipe.
Larger bend radii can be achieved using the so-called melting cores which, however, due to difficult handling and problems related to temperature, and not least the high costs for this area of application, have not been successful in practice--also considering that an automatic run of such tools is not realistic. The last point also applies to the so-called insertion cores the dimensions of which narrow down the band of application to a great extent i.e. a perfect demoulding is no longer possible for slightly longer straight pipe terminal portions of approx. 0.5 D.
The invention aims at overcoming the above described defects by the creation of an appropriate injection moulding core for pipe bends.
The solution to the task thus set is shown in the claims.
One embodiment of the invention is described using the drawings. These show the following in detail:
FIG. 1 the side view of an injection moulding core according to the invention in distended position,
FIG. 2 the side view of the injection moulding core for the bend core from FIG. 1 and
FIG. 3 the side view of this injection moulding core during demoulding.
As is shown in FIG. 1, the injection moulding core described here for pipe bends with straight terminal portions is divided in individual segments a, vertical to the medial line b of the bend, and preferably in twelve parts for a bend of 90.degree.. These segments a are connected to a chain with the aid of mushroom-shaped projections c. Since, owing to the larger outer diameter and the smaller internal radius of the bend core, the individual segments a have wedge-shaped side views, these projections c must be formed in such a way that with distended chain the medial line b of the segments a form a straight line. The individual segments a are, furthermore, mutually fixed by conical centering pins d in order to avoid any displacement or torsion. Furthermore, the segments a comprise one or several bores through which pass the metal cables f as traction elements which are connected to the last segment a of the bend core by fixing elements g. At its other end the chain of segments adjoins onto the core h for the straight pipe terminal portion by means of the metal cables f passing through this core, their ends being connected to displacement elements i, as for example to a spindle or to a hydraulic cylinder.
FIG. 2 shows the condition of the chain of segments after the metal cables f have been passed by means of the displacement elements i to the end position k. The segments a have arranged themselves to the bend core 1 according to their wedge-shape. They are finally fixed in position by being brought against the core m for the second straight pipe terminal portion so that the metal cables f predominantly assume the kinetic part of the operation whilst locking is effected by the cores h and m. The centering pins d or other suitable elements prevent the segments a from being pushed from the connection whereby these elements must be conceived for a stress of P x cos .alpha./2.
FIG. 3 shows the injection moulding core according to the invention during the demoulding process. It can be seen here that removal of the bend core 1 is synchronized with the motion of the displacement elements 1 and the metal cables f accordingly. By way of example, the demoulding conicity with wedge-shape of 7.5.degree. must be equal to 0.03 % of the bend internal radius per bend degree.
1. Injection molding core for pipe bends having at least o
REFERENCES:
patent: 223820 (1880-01-01), Shehan
patent: 3095613 (1963-07-01), Christensen et al.
patent: 3417601 (1968-12-01), Werner
patent: 3545718 (1970-12-01), Shale
Agru Alois Gruber & Sohn Offene Handelsgesellschaft
Batten, Jr. J. Reed
Crosby Gene P.
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