Apparatus for moulding plastic products

Abstract: The invention relates to an apparatus for moulding plastic products (31' - 36'), said apparatus comprising at least two plastic moulding machines (1', 2') each of which comprises a robot (7' - 8') for transferring a moulded product (31', 32') from the moulding machine onto a conveyor belt (30'). In order to significantly facilitate and expedite quality inspection and thus also to allow any quality defects to be rapidly corrected, and in order to considerably simplify the transport of the products and the structure of the apparatus, said at least two moulding machines (1', 2') are mounted along a common conveyor belt (30') substantially successively on the same side of the belt, whereby their robots (7', 8') are arranged to place the moulded products (31', 32') at different points over the width of the belt.

Description: The invention relates to an apparatus for moulding plastic products, said apparatus comprising at least two plastic moulding machines each of which comprises a robot for transferring a moulded product from the moulding machine onto a conveyor belt. Apparatuses of this kind are well known. Moulding machines are typically injection moulding machines. They are used, for example, for moulding parts of plastic enclosures. Each injection moulding machine is typically used for moulding one type of products, e.g. the bottom or the cover of a plastic enclosure; after the moulding, the parts are combined to form a plastic enclosure. Moulded products must satisfy certain quality criteria - often rather strict ones - as regards the surface, for example. The quality of products can often be quite easily determined on the basis of ocular assessment when the products are on the conveyor belt to which they are ejected from the injection moulding machine. Since there are several injection moulding machines located in different parts of the factory hall, the person responsible for quality inspection must go from one machine to another; this is because it is not sensible to have different persons inspecting the quality of products produced by the different injection moulding machines. In practice, the person responsible for quality inspection has to "run" from one machine to another. Another factor that makes it more difficult to do the job rationally is that the moulding time, i.e. the time it takes to manufacture a product, is different at the different injection moulding machines: one machine may use e.g. two seconds for the manufacture of a product, another one may use eight seconds, yet another one needs nine seconds, etc. On account of this, the person responsible for quality inspection must go to the different injection moulding machines at different intervals, depending on the machine and the product. On account of the arrangement described above, a defect in the quality of a product is detected at a relatively late stage. An injection moulding machine may mould a large number of defective products before the defect is detected and the machine is stopped so that the necessary steps can be taken to correct the defect. Another problem associated with known apparatuses comprising several moulding machines is removing products from the machines and transporting them for further treatment or packaging. This requires that either a motor-driven forklift or a hand pallet truck is used for collecting the moulded products, which are normally piled on a pallet, separately from each moulding machine. When there are several injection moulding machines located in different parts of the factory hall, the truck has to travel relatively long distances, which not only consumes time and energy but also increases the risk of accidents. Yet another problem with apparatuses comprising several moulding machines is that they take up a lot of floor area in a factory hall. It has not been possible to mount the machines close to each other, since narrow passages between the machines would complicate the transport of moulded products with a forklift. GB-A-2 204 267 discloses an apparatus for moulding plastic products, said apparatus comprising a plurality of separate plastic moulding machines mounted along a common conveyor belt substantially successively on the same side of the belt, each of which comprising a robot for transferring a moulded product from the moulding machine onto the belt. The delivery of the moulded products onto the belt is controlled to prevent a product from one machine from colliding with a product from another machine. The object of the present invention is to obviate the problems described above. This can be achieved with an apparatus according to claim 1 of the present invention. There are preferably a plurality of moulding machines mounted in succession along the belt, which renders the invention particularly advantageous. Preferred embodiments of the invention are disclosed in appended claims 2 to 4. The present invention is based on the idea of mounting a plurality of moulding machines in succession along a common conveyor belt so that they eject the moulded products onto the same belt. So far it has been thought that such an arrangement cannot work in practice in the plastics industries, because different products and moulding machines have different moulding times: if several moulding machines with different moulding times were mounted in succession, the products would be in disorder and on top of each other at some points of the conveyor belt. According to the invention, it has been surprisingly discovered that moulding machines with different moulding times can be mounted in succession without any problems if separate zones are reserved for the different products in the transverse direction of the conveyor belt. To this end, the common conveyor belt is made so wide that a number of product types corresponding to the number of moulding machines can be ejected thereto without any danger of adjacent products coming into contact with each other. The most significant advantages of the present invention are that it facilitates and expedites quality inspection considerably, whereby any defects in quality can be more rapidly corrected, and that the transport of the products becomes considerably less complicated and more economical at the same time that the security is improved. In addition, the apparatus is less complicated in structure and less expensive than known apparatuses, since several conveyor belts are not needed. In the following, the invention will be described in greater detail with reference to the accompanying drawing, in which Figure 1 shows an apparatus of the prior art, and Figure 2 shows an apparatus of the invention. The apparatus according to Figure 1 comprises six injection moulding machines 1 to 6 for moulding components of plastic enclosures. Each of the machines 1 to 6 manufactures a different plastic product. Each moulding machine 1 to 6 comprises a robot 7 to 12 for transferring the moulded product onto the conveyor belt 13 to 18. Reference numerals 19 to 24 indicate the position of the machine operator. The products are removed from the belts 13 to 18 in the direction of the arrows. The person responsible for quality inspection goes to each belt 13 to 18 so as to detect any defects in quality. It is usually impossible for him to follow any predetermined route from one moulding machine to another. He may go, for instance, from machine 1 to machine 2, from machine 2 to machine 3, from machine 3 to machine 6, from machine 6 to machine 10, from machine 10 to machine 11, from machine 11 to machine 1. However, this order cannot remain unchanged for several reasons: interruption in the production of some moulding machine(s), different moulding times, etc. If the person responsible for quality inspection follows the above-mentioned route, and a defect occurs in the production of moulding machine 2 soon after he has inspected the quality of the products of machine 2, he will not return to machine 2 until after he has inspected the quality of the products of machines 3, 6, 10, 11 and 1. The delay may be rather long, in which case moulding machine 2 produces a large number of defective products until it is stopped, whereafter the detected defect can be corrected. The products supplied from the belts are piled on separate pallets (not shown), from which they are transported to a further treatment station 25 as shown by the curved arrows, or directly into storage (not shown). The layout of Figure 1 shows that there must be a sufficiently wide passage for a forklift between moulding machines 2 and 3, and 5 and 6. Figure 2 shows an apparatus of the invention. The apparatus produces the same products as the apparatus of Figure 1. For reasons of simplicity and clarity, the reference numerals in Figure 2 are similar to those in Figure 1. In Figure 2, the moulding machines 1' to 6' are arranged on both sides of a common conveyor belt 30'. Moulding machines 1' to 3', mounted in succession on one side of the belt 30', are arranged to eject their products 31' to 33' to different points over the width of the belt. The same applies to moulding machines 4' to 6', and thus the belt can be considered to be divided into six zones. In the case of Figure 2, the robot 7' of moulding machine 1' ejects its product 31' to one edge of the belt 30'; the robot 8' of moulding machine 2' ejects its product 32', whose moulding time on the basis of products 31', 32' is twice as long as that of product 31', to belt zone 30', which is adjacent to the zone reserved for product 31'; the robot 9' of moulding machine 3' ejects its product 33' to a zone which is close to the centre line of the belt 30'. Correspondingly, the robot 10' of moulding machine 4' ejects its product 34' to a zone which is close to the centre line of the belt 30', but on the opposite side thereof to the zone reserved for product 33'. The robot 12' of moulding machine 6' ejects its product 36' to the other edge of the belt 30'; the robot 11' of moulding machine 5' ejects its product 35' to a zone which is adjacent to the zone reserved for product 36'. It can be seen from Figure 2 that all the products 31' to 36' have different moulding times, but still they have a common conveyor belt 30'. It is therefore very easy for the person responsible for quality inspection to monitor the quality of all products 31' to 36' on the belt 30' from an inspection station 40', although the number of products per a unit of time varies. If the person detects a defect in product 32', for example, he is able to inform the operator of moulding machine 2' of it very quickly so that the defect in moulding machine 2' can be corrected. In addition to inspecting the quality, the person responsible for quality inspection can also sort the different products into different piles. The arrangement of Figure 2 allows the products to be further transported with a forklift from the inspection and sorting station 40' e.g. to a further treatment station 25 or into storage (not shown) by the most direct route; the forklift does not have to travel from one moulding machine to another. The moulding machines of Figures 1 and 2 are injection moulding machines, but it is also conceivable to employ other types of plastic moulding machines. In the above, the invention has been described only by means of an example. It will be clear to one skilled in the art that in its details the apparatus of the invention can differ to a great extent from the one shown in Figure 2. For example, the number of the moulding machines may thus be different, and the machines may be located either on both sides or on only one side of the belt 30'.

Claims: An apparatus for moulding plastic products (31', 32'), said apparatus comprising at least two separate plastic moulding machines (1', 2') with different moulding times mounted along a common conveyor belt (30') substantially successively on the same side of the belt, each of which comprising a robot (7', 8') for transferring a moulded product (31', 32') from the moulding machine onto the belt (30') the robots (7', 8') being arranged to place the moulded products (31', 32') at different rates and at different points over the width of the belt. An apparatus according to claim 1, characterized in that it comprises a third moulding machine (4') mounted on the opposite side of the conveyor belt (30') to said at least two moulding machines (1', 2'), the robot (10') of said third moulding machine being arranged to eject the product (34') moulded in the third moulding machine to a different point of the width of the belt than the robots (7', 8') of said at least two moulding machines. An apparatus according to claim 2, characterized in that it comprises a fourth moulding machine (5') mounted substantially after said third moulding machine (4') in the longitudinal direction of the belt (30'), the robot (11') of said fourth moulding machine being arranged to eject the product (35') moulded in the fourth moulding machine to a different point of the width of the belt than the robots (7', 8', 10') of said at least two and said third moulding machines (1', 2', 4'). An apparatus according to any one of the preceding claims, characterized in that the moulding machines are injection moulding machines (1' - 6').

Inventors: AIRAS RISTO, EILOMAA MIKA, TIRRONEN TIMO, AIRAS, RISTO, EILOMAA, MIKA, TIRRONEN, TIMO
Applicants: FIBOX OY AB
Application year: 1996
Main classification: B29C45
IPC codes: B29C45, B29C37, B29C31