Technical Field

The invention is a modular injection mould comprising two plates, wherein one of the plates is connected to a source of external force.

Background Art

Plastic injection moulding is a relatively conventional method of manufacturing plastic products. It is typical for mass production. The process takes place in cycles on an injection moulding machine. One cycle is the sum of all the necessary operations required for one injection into the mould. Depending on the multiplicity of the mould a corresponding number of parts are produced per injection. Often there is one injection mould for one product shape.

The injection mould must be prepared before injection moulding. The mould is assembled and checked outside the machine. It is then clamped into the movable and rigid mounting plate of the machine. This is followed by centring the two parts of the mould relative to each other. Once these operations are completed, the mould is ready for injection moulding.

If a change in the injection is required, the injection mould must also be changed. In the conventional approach, the mould must be removed from the machine. Once the mould is out of the machine, changes can be made. Injection moulds are standardised. If the mould design adheres to the standards, changing the mould is easier. This means that some parts from the previous mould can be used for the new mould. The mould is then placed and centred on the injection press.

Removing, changing, mounting and centering the injection mould are time consuming activities. However, it is not always necessary to make changes that require the entire injection mould to be removed. Sometimes it is sufficient to change only the shape of the mould cavity. The cavity has a negative shape enlarged to allow for shrinkage of the injected component

From patent file US20100092706A1 , an injection mould for injecting an object having a base and a side wall is known, the injection mould including a first mould part and a second mould part that are designed to be joined together in a closed configuration to define a mould cavity between them, the mould cavity having a base part and a side wall part, the injector for injecting molten material into the mould cavity, which is to be moulded into a product, wherein at least one portion of one of the first and second mould portions is movable when the first and second mould portions are in a closed configuration so as to vary the volume of the mould cavity, an actuator for selectively moving at least one portion of one of the first and second mould portions in the first and second directions so as to increase and decrease, respectively, the volume of the mould.

The state of the art is further represented by US20120177772A1 , US6165407A, US20090302490A1 or US20120171317A1.

Disclosure of Invention

The essence of the invention is a modular injection mould comprising two plates, wherein one of the plates is connected to a source of external force. This plate is movable and is adapted for the insertion of a removable insert, wherein the insert does not extend beyond the front surface of the movable plate facing the second plate, the removable insert comprising at least one cavity.

Preferably, the insert comprises at least two segments, wherein at least one segment has a cavity. The insert with the cavity has its cavity volume increased by the shrinkage value of the injection moulded part. If the injection moulded part has a small volume, the cavity of the insert or in the segment from which the removable insert is formed will also be small. The other segments then only fill the volume of the movable moulding plate by their shape. If the size of the other segments is chosen correctly, it is sufficient to produce only a segment with a cavity for the new part. This segment will have a significantly smaller volume than the volume of the entire moulding plate.

It is further advantageous if the material of the insert is different from that of the plates. There is a large range of available plate materials, from hard metals to plastics, thus it is possible to select a material whose properties, in particular durability, will be sufficient for the planned number of injection moulded pieces. At the same time, its processing and price will usually be more advantageous.

The insert is fixed in the plate by a frame connected to the plate, which does not extend beyond the surface of the opposite plate. This simple connection enables a quick change of inserts. If the screws are tightened correctly, there is no risk of uneven alignment of the frame against the moulding plate, which could cause overflow into the partition plane

It is also advantageous if the insert contains internal channels. This allows the temperature control system to be adjusted if the temperature control channels are part of a replaceable cavity. This change can be made directly on the injection press without the need for removal, fitting, centering, etc. This reduces the time required to change the injection mould.

An injection mould with the ability to change the cavity directly on the injection moulding machine is referred to as a modular injection mould. Cavities and backing plates are individual modules. The modular injection mould is based on the convection type of mould. Most of the mould is clamped on the machine and is not removed from the machine when the cavity is changed. The change to a different cavity takes place in the design modification which is a claim for patent protection.

Compared to a conventional insert injection mould, the inserts of a modular injection mould are clamped entirely from the injection plane. The cavities can thus be replaced by moving the mounting plates of the injection press directly on the machine. The modular injection mould should only be used on injection moulding machines that allow the machine mounting plates to be spaced far apart.

Description of drawings

Fig. 1 shows a cross-section of an injection mould. Fig. 2 shows the mould including the moving parts of the modular injection mould. Fig. 3 shows the fixed and movable main plate. The modification by milling of the space for removable parts is the essence of the Modular Injection Mould. Fig. 4 shows a specific embodiment of the insert consisting of individual segments

Description of example embodiment

The modular injection mould comprises two plates 1 and 2. Plate 1 is connected to an external force source Z. Plate 2 is movable and hollow and is adapted for inserting a backing plate \T. A removable insert V made of carbide is inserted into the movable plate 2 from above. The removable insert V is supported by the backing plate \T- The insert V does not extend over the front surface of the movable plate 2 facing plate 1. An injector passes through the hole in plate 1. The removable insert V in this exemplary embodiment comprises four segments S, one segment S being provided with a cavity D. The material of the insert V is different from the material of plates 1_ and 2. The insert V is fixed in plate 2 by a frame R connected to movable plate 2 in such a way that it does not overlap the surface of movable plate 2 facing plate 1. The frame R is attached to movable plate 2 by screws. The insert V is provided with channels K in which the cooling medium flows.

The relative movement of the movable plate 2 towards plate 1 brings the faces of the two plates 1 and 2 into contact with each other. The material is injected by an injector through a hole formed in plate 1_ into the cavitation cavity D located in the insert V. Insert V is cooled by a cooling medium flowing through channels K formed in the insert V. The outlet of these channels K is connected to the temperature system in movable plate 2. After the injection of the material from the injector into the cavity D, plates 1 and 2 are separated from each other and the piece is subsequently removed. The modularity of the segments S ensures that the number of segments containing the cavitation cavity D is variable. By loosening the screws, the frame R can be removed and the individual segments S can be removed and replaced as required. For ease of removal, the outer edges of the S segments are chamfered. After subsequent tightening of the frame R, injection moulding of different shaped parts can be carried out again.

Industrial applicability

The modular injection mould can be used in injection moulding applications where the shape of the cavity in the mould needs to be changed frequently. If necessary, the cooling system can be changed, provided that there are cooling channels in the cavity. The modular injection mould allows for changing individual cavities, i.e. modules. The application of the modular injection mould is suitable for prototype or small series production and especially for verification of the shape of the cavity of the injection mould.