GB1592207A - Collapsible cores for the manufacture of moulded components - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO COLLAPSIBLE CORES FOR THE MANUFACTURE OF MOULDED COMPONENTS (71) We, GEYER, WERKZEUGBAU GMBH & CO KG, formerly known as GEYER & CO., of Königsberger Strasse 11, D-5889 Liidenscheid, Germany, a German Kommanditgesellschaft, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to'bye performed, to be particularly described in and by the following statement: This invention relates to a collapsible core usable, for example, in the manufacture of moulded components. In particular, the invention relates to a collapsible core comprising an elongated core member and a longitudinally segmented casing whose segments are arranged to move axially and radially over the core member from an operative state for use in the moulding process to a state in which the moulded component can conveniently be removed and vice versa.

Collapsible cores allow plastics components, for example, to be injection moulded, and such components can be manufactured with internal screw threads, nozzles, internal cavities, grooves, notches, apertures and undercuts. The outer surfaces of the segmented casing determine, in the operative state, the shape of the inner wall of the component. Since the inner wall has undercuts, the outer diameter of the casing must be reduced to allow removal of the component after moulding. Separation of the component from known collapsible cores is often incomplete.

In accordance with the present invention, there is provided a collapsible core comprising an elongated core member and a casing divided longitudinally into segments slidable axially and radially over the external surface of the core member, the said external surface of the core member being divided longitudinally into two groups of conical surface portions, of which the surface portions of one group have a larger cone angle than an alternate circumferentially with the surface portions of the second group, and the said casing segments being divided into two groups, the segments of the first group being arranged one on each of the surface portions of said one such group and having a trapezoidal- cross-sectional shape and the segments of the second group being arranged one on each of the surface portions of said second such group and having the cross-sectional shape of a segment of a circle, the segments being so shaped that the non-parallel sides of the trapezoidallyshaped segments are in contact with the radially inner chordal bases of the adjacent segments during relative movement thereof to and from an operative state of the core and that, in the operative state of the core, the end faces of the two groups of casing segments lie in the same plane as the end face of the core member.

The collapsible core of the present invention allows manufacture of components with rounded or rectangular cross-sections, for example, which also may have complex undercuts.

Only a small number of segments of each group are required and different ones may be used with the same core member to provide collapsible cores for producing mouldings of different diameters, or other lateral dimension. The segments are moved radially inwards towards each other by their movement axially of the core member, so that deep undercuts can be produced in a moulded component, and the undercuts can be of any required shape, for example rounded or angular. No burrs are formed on the finished article, which can be produced to a high degree of accuracy.

The synchronisation of the slidable segments minimizes wear and tear of the core and thus lengthens its lifetime.

Large equipment is not required in order to set up the core for operation; its assembly is simple and cheap, and there is no restriction due to the core construction on the maximum lateral dimension of a component to be produced.

The elongate core member allows a cooling bore to be provided and to extend to its free end, adjacent the core region at which formation of the component takes place.

By appropriate choice of material, the collapsible core can be used for thermoplastic manufacture, duroplastic manufacture, metal die casting, and for piercing and stamping.

Since no additional connections are required to the core, it can be used with almost any form of injection moulding apparatus.

Several embodiments of collapsible cores for the manufacture of injection moulded components, each in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure la is a cross-sectional, elevational view, along the line W-W of Figure ib, of one embodiment of the core, in the operative injection moulding state; Figure ib is an axial end view in the direction of arrow Y of Figure la; Figure 2a is a view similar to that of Figure la, along the line W-W of Figure 2b, showing the core in the inoperable moulded article removing state; Figure 2b is a view similar to that of Figure ib, in the direction of the arrow Y of Figure 2a; Figure 3 is a cross-sectional view similar to that of Figure la of an alternative core, having an additional centre core portion in the operative injection moulding state; Figure 4 is a view similar to, and showing the same embodiment as Figure 3, in the inoperative, non-moulding state; Figure 5a is an elevational, cross-sectional view of another embodiment of a core, in the operative injection moulding state and installed in a moulding tool, along the line W-W of Figure 5b; Figure 5b is an axial end view in the direction of the arrow Y of Figure 5a;.

The collapsible core as shown in Figures 1-5 includes an elongated core member in the form of a core pin 1 and two groups of casing segments in the form of lateral or flanking slides 2 and 3 arranged around the core pin. All of the lateral slides belonging to the same group are of identical structure.

The illustrated embodiment has three slides in each group. Each of the lateral slides 2 alternates with successive lateral slides 3, around the circumference of core pin 1.

Core pin 1 may contain an additional centre core 4, as shown in Figures 3 and 4. One or a plurality of expanding cores are components of a moulding tool 5, as shown in Figures 5a and 5b.

At one of its ends, core pin 1 is shaped to constitute a connecting part 11 for making a connection with a stationary part 51 of the moulding tool 5. At the free end of connecting part 11, a thread 12 is provided. A central cooling- bore 13 ' passes through substantially the entire core pin 1 from the outer end face of part 11 to the region of the opposite end face of part 11 to the region of the opposite end face of core pin 1.

In the embodiments shown in Figures 1 to 5, the core pin 1 is provided with a conical outer surface in the form of a pyramidal frustum having alternating surface portions or faces 14 and 15 and located beyond conncting part 11. The slope of the faces 15, which is determined by the angle ss formed with the axis of the pin, is greater than that of faces 14, which is determined by the angle a, also formed with the pin axis. In the illustrated embodiment, ss is about twice as large as a.

Slides 2 are.mounted to slide along the faces 14, while slides 3 are mounted to slide along the faces 15. In order to hold lateral slides 2 and 3, each of faces 14 and 15 is provided with a dovetail mortise, or groove, 16 and 17, respectively. The faces 14 and 15 and their associated mortises 16 and 17 begin at the connecting part 11 and end at that end face of core pin 1 which is remote from the connecting part 11.

Each of the lateral slides 2,which slide along the faces 14 of core pin 1 while being guided in grooves 16, has a cross-section which has essentially the shape of a segment of a circle. The chordal base 21 of each such segment is interrupted by a dovetail tenon, or rib, 22 which engages in its associated groove 16. At its free end, directed away from connecting part 11, each lateral slide 2 is provided with an extension 24 whose outer surface 25 defines the inner wall of the injection moulding cavity which is to be formed by the core. In the illustrated embodiment the outer surface 25 is provided with parallel grooves.

At a point spaced from extension 24, each lateral slide 2 is provided with a part 26 of an annular collar by which the axial movement of the lateral slides 2 within the moulding tool 5 is effected.

The lateral slides 3, which slide along the sloping faces 15 of core pin 1 and are guided in grooves 17, have a cross-sectional shape which is essentially that of a trapezoid whose outer base 31 has a curvature which corresponds to the curvature of the circular segments of the lateral slides 2 adjacent thereto. The other, larger, base 32 of each slide 3 is interrupted by a dovetail tenon, or rib, 33 with which the lateral slide 3 is guided in an associated groove 17. The lateral sides of each slide 3 which correspond to the non-parallel sides of the trapezoidal cross section contact the surfaces defined by the chordal bases 21 of respective adjacent lateral slides 2.

Each lateral slide 3 is also provided with an extension 34 at its free end directed away from part 11, the outer surface 35 of this extension conforming to the shape of the inner wall of the injection moulding cavity to be established. At a point spaced from the outer surface 35 each lateral slide 3 is also provided with a part 36 of the annular collar. Parts 26 and 36 form the complete annular collar. This collar is provided to effect the axial movement of the lateral slides 2 and 3 within the moulding tool 5.

In the embodiment shown in Figures 3 and 4, the core pin 1 itself is designed as a hollow body portion with an open frontal end. The hollow body is filled by an internal core which is introduced into the pin via the open frontal end. Head 41 of the internal core 4 serves as a part of the mould core and is designed to correspond to the configuration of a recess in the moulded piece to be produced. If the core pin 1 is provided with such an internal core 4, a cooling bore 42 is advantageously provided within the centre core 4 and extends axially into the region of head 41. With this construction it is possible to provide, further extensions beyond an undercut, e.g. cylindrical extensions, which may also have axial perforations.

In the embodiments of both Figures 1 and 2 and 3 and 4 the free end faces of the slides 2 and 3 lie in the operative state of the core, in the same plane as the end face of the core pin 1.

The moulding tool 5, of which only the machine side is shown in Figures 5a and 5b, is a conventional moulding tool having a base plate 51 to which the core pin 1 is screwed, two slide guide plates 52 and 53, and a stripping or skimmer plate 54. Removal of the core from the moulded part is effectuated by moving plate 51 away from plates 52, 53 and 54, thereby causing slides 2 and 3 to move radially inwardly, and by then separating the moulded part from the core.

As is readily apparent from a consideration of Figures la, ib, 2a and 2b, the slides 2 and 3 are formed such that, aside from the regions of collar parts 26 and 36, the length of chordal base 21 of each slide 2 and the length of the large base 32 of each slide 3 decreases progressively along the length of pin 1 in the direction toward connecting part 11.

In the operative moulding state, i.e. the state shown in Figures 1 and 3, all extensions 24 and 34, and possibly the head 41 of the internal core 4, form the mould core for producing an internal wall in the moulded part.

The collapsible core shown in Figures 1 to 5 operates as follows: after the mould is opened the slide guide plates 52, 53 are moved together with stripping plate 54 upwardly in the axial direction through-the distance S shown in Figure 2a. The slide guide plates 52, 53 are screwed dr otherwise secured together and can travel the distance S. Since the core pin 1 is firmly secured to the stationary base plate 51, 'the lateral slides 2 and 3 which have been carried along via collar 26, 36 also traverse a length S.

Since the angle a which determines the slope of the outer surface portions 14 is about half as large as the angle ss which determines the slope of the outer surface portions 15 of core pin 1, the lateral slides 3 not only slide the length S in the axial direction, but they also slide inwardly along the surfaces defined by chords 21 on the adjacent lateral slides 2. This permits the lateral slides 2 to move along the -conical outer surface portions 14 of core pin 1.

At the end of the axial movement S, the inner edges at the free end of the lateral slides 3 have been displaced radially inwardly by a distance which', due to the relationship ss=2a, is twice as great, with respect to their starting position, as the inward radial displacement of the inner edges at the free end of lateral slides 2. Whereas inner edges of the free ends of slides 2 and 3 are equidistant from the axis of pin 1 in the injection moulding state, the distance S1 of the inner edges of lateral slides 3 is less than the distance S2 of the inner edges of the lateral slides 2 in the inoperative state.

After slides 2 and 3 have traversed distance S, the moulded part is freed from lateral slides 2 and 3 due to their paiallel axial and radial movements toward the inside. The largest outer diameter of the parts of lateral slides 2 and 3 which define the actual mould core is then, in the inoperative state, less than the smallest inner diameter of the recess formed in the moulded part. Thus the moulded part can be removed from-the moulding tool by the action of stripping plate 54.

Upon return of the moulding tool 5 to its starting position, the lateral slides 2 and 3 slide back along the core pin 1 to their starting positions. A new injection moulding process can then be initiated: Here it is of advantage to arrange the moulding tool as a multiplate tool, i.e. to provide it with a plurality of collapsible cores.

WHAT WE CLAIM IS: I. A collapsible core comprising an elongate core member and a casing divided longitudinally into segments slidable axially and radially over the external surface of the core member, the said external surface of the core member being divided longitudinally into two groups of conical surface por

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   lateral sides of each slide 3 which correspond to the non-parallel sides of the trapezoidal cross section contact the surfaces defined by the chordal bases 21 of respective adjacent lateral slides 2.

   Each lateral slide 3 is also provided with an extension 34 at its free end directed away from part 11, the outer surface 35 of this extension conforming to the shape of the inner wall of the injection moulding cavity to be established. At a point spaced from the outer surface 35 each lateral slide 3 is also provided with a part 36 of the annular collar. Parts 26 and 36 form the complete annular collar. This collar is provided to effect the axial movement of the lateral slides 2 and 3 within the moulding tool 5.

   In the embodiment shown in Figures 3 and 4, the core pin 1 itself is designed as a hollow body portion with an open frontal end. The hollow body is filled by an internal core which is introduced into the pin via the open frontal end. Head 41 of the internal core 4 serves as a part of the mould core and is designed to correspond to the configuration of a recess in the moulded piece to be produced. If the core pin 1 is provided with such an internal core 4, a cooling bore 42 is advantageously provided within the centre core 4 and extends axially into the region of head 41. With this construction it is possible to provide, further extensions beyond an undercut, e.g. cylindrical extensions, which may also have axial perforations.

   In the embodiments of both Figures 1 and 2 and 3 and 4 the free end faces of the slides 2 and 3 lie in the operative state of the core, in the same plane as the end face of the core pin 1.

   The moulding tool 5, of which only the machine side is shown in Figures 5a and 5b, is a conventional moulding tool having a base plate 51 to which the core pin 1 is screwed, two slide guide plates 52 and 53, and a stripping or skimmer plate 54. Removal of the core from the moulded part is effectuated by moving plate 51 away from plates 52, 53 and 54, thereby causing slides 2 and 3 to move radially inwardly, and by then separating the moulded part from the core.

   As is readily apparent from a consideration of Figures la, ib, 2a and 2b, the slides 2 and 3 are formed such that, aside from the regions of collar parts 26 and 36, the length of chordal base 21 of each slide 2 and the length of the large base 32 of each slide 3 decreases progressively along the length of pin 1 in the direction toward connecting part 11.

   In the operative moulding state, i.e. the state shown in Figures 1 and 3, all extensions 24 and 34, and possibly the head 41 of the internal core 4, form the mould core for producing an internal wall in the moulded part.

   The collapsible core shown in Figures 1 to 5 operates as follows: after the mould is opened the slide guide plates 52, 53 are moved together with stripping plate 54 upwardly in the axial direction through-the distance S shown in Figure 2a. The slide guide plates 52, 53 are screwed dr otherwise secured together and can travel the distance S. Since the core pin 1 is firmly secured to the stationary base plate 51, 'the lateral slides 2 and 3 which have been carried along via collar 26, 36 also traverse a length S.

   Since the angle a which determines the slope of the outer surface portions 14 is about half as large as the angle ss which determines the slope of the outer surface portions 15 of core pin 1, the lateral slides 3 not only slide the length S in the axial direction, but they also slide inwardly along the surfaces defined by chords 21 on the adjacent lateral slides 2. This permits the lateral slides 2 to move along the -conical outer surface portions 14 of core pin 1.

   At the end of the axial movement S, the inner edges at the free end of the lateral slides 3 have been displaced radially inwardly by a distance which', due to the relationship ss=2a, is twice as great, with respect to their starting position, as the inward radial displacement of the inner edges at the free end of lateral slides 2. Whereas inner edges of the free ends of slides 2 and 3 are equidistant from the axis of pin 1 in the injection moulding state, the distance S1 of the inner edges of lateral slides 3 is less than the distance S2 of the inner edges of the lateral slides 2 in the inoperative state.

   After slides 2 and 3 have traversed distance S, the moulded part is freed from lateral slides 2 and 3 due to their paiallel axial and radial movements toward the inside. The largest outer diameter of the parts of lateral slides 2 and 3 which define the actual mould core is then, in the inoperative state, less than the smallest inner diameter of the recess formed in the moulded part. Thus the moulded part can be removed from-the moulding tool by the action of stripping plate 54.

   Upon return of the moulding tool 5 to its starting position, the lateral slides 2 and 3 slide back along the core pin 1 to their starting positions. A new injection moulding process can then be initiated: Here it is of advantage to arrange the moulding tool as a multiplate tool, i.e. to provide it with a plurality of collapsible cores.

   WHAT WE CLAIM IS: I. A collapsible core comprising an elongate core member and a casing divided longitudinally into segments slidable axially and radially over the external surface of the core member, the said external surface of the core member being divided longitudinally into two groups of conical surface por

   tions, of which the surface portions of one group have a larger cone angle than and alternate circumferentially with the surface portions of the second group, and the said casing segments being divided into two groups, the segments of the first group being arranged one on each of the surface portions of said one such group and having a trapezoidal cross-sectional shape and the segments of the second group being arranged one on each of the surface portions of said second such group and having the crosssectional shape of a segment of a circle, the segments being so shaped that the nonparallel sides of the trapezoidally-shaped segments are in contact with the radially inner chordal bases of the adjacent segments during relative movement thereof to and from an operative state of the core and that, in the operative state of the core, the end faces of the two groups of casing segments lie in the same plane as the end face of the core member.
2. 2. A collapsible core according to claim 1, wherein each segment is slidably retained by a dovetailed groove extending along the associated surface portion of the core member.
3. 3. A collapsible core according to claim 1 or claim 2, wherein the core member is in the form of a hollow outer body portion and an internal core portion is located therein.
4. 4. A collapsible core according to any preceding claim, wherein the core member has a cooling bore extending therewithin.
5. 5. A collapsible core substantially as hereinbefore described with reference to the accompanying drawings.