Abstract:
A plant for producing products assembled of injection-molded plastic components. The plant includes a conveying system with one or more rails for conveying the components through the plant, a longitudinal groove formed in each rail for accommodating at least one suspension part of each of the sprues used for injection-molding the components, and a member for slidably displacing the suspension parts in the longitudinal grooves while the sprues are still connected with their components. The plant has a simple and inexpensive construction while also providing a very high production rate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation of International application PCT/EP2004/000617 filed Jan. 26, 2004, the entire content of each of which is expressly incorporated herein by reference thereto. 
     
    
     BACKGROUND ART  
       [0002]     The invention relates to a method for transporting and/or assembling injection molded components, and a plant for producing products assembled of injection-molded plastic components, comprising at least two injection-molding machines and an assembling station for assembling the components.  
         [0003]     Very many products are assembled of injection-molded plastic components of different kinds. Each kind of component is injection-molded by means of a special mold mounted in an injection-molding machine. The finished components are normally collected in a casing. The same machine is also often used to injection-mold the other components or some of them. The casings with the components are then transported to a station for separating the components from their sprues and thereafter to an assembling station where the components are manually and/or by means of robots assembled to the finished product. The handling and assembling of the components in this way, however, is very labor-intensive and costly and moreover the production capacity is relatively low.  
         [0004]     When a larger capacity is desired, one or more injection-molding machine is used for each component. The production rates of these machines are preferably the same thereby ensuring that the different components can be both separated from their sprues and arrive at an assembling station at the same time. Thereby is it possible to successively assemble the components in the same sequence as they arrive at the assembling station.  
         [0005]     The production capacity is, however, limited by the possible production rate at the separation station and assembling station. This production rate is relatively low, since the different components arrive to the stations in an unarranged orientation and therefore first need to be correctly orientated. The separation and assembling of the components is therefore also relatively labor-intensive and costly in this case.  
         [0006]     To avoid separation of the components the U.S. Pat. No. 6,360,899 discloses the production of a number of injection-molded components with a common sprue. The components are not separated from the sprue but are sold as one piece. The pieces are separated from the sprue by the end user and used as light holders. The sprue is used as a cord wrap. No assembly of the components is performed and how the sprue is transported is not discussed in this document.  
         [0007]     European patent application 1,164,000 describes a method for manufacturing an optical disc. The optical disc described herein comprises two disc halves, which are bonded together to form a single disc at an assembly station. The two halves are provided from separate injection molding units. This is a very specific manufacturing method suited for optical discs and the document is furthermore silent on how and where the disc halves are separated from their sprues.  
         [0008]     British patent 701452 discloses a method for injection-molding and assembling parts. In order to avoid variations in tolerances, mating parts in an assembly are produced in the same mold and thereby receive a common sprue. The parts are afterwards one by one stamped out of the sprue in a machine and assembled with its mating part. By producing two different parts in one mold, however, the production of the molds gets expensive and if one of the parts needs to be modified the whole mold needs to be replaced. Likewise if an assembly consists of more than two parts the molds would be very costly to produce since all the parts need be formed in a single mold.  
         [0009]     Thus, improvements in these type devices is desired.  
       SUMMARY OF THE INVENTION  
       [0010]     In one aspect of the invention a method is provided for in an easy and an expedient way transporting and/or assembling inject-molded plastic components by means of the sprue originally connected to the components.  
         [0011]     In another aspect according to the invention, a plant is provided of the type mentioned in the opening paragraph, but which is less labor-intensive and costly than known hitherto.  
         [0012]     In third aspect according to the invention, a plant is provided of the type mentioned in the opening paragraph, but which has a higher production rate than known hitherto.  
         [0013]     In a forth aspect according to the invention, a plant is provided of the type mentioned in the opening paragraph, but which has a simple, cheap and effective conveying system for conveying the components of the products through the plant.  
         [0014]     In a fifth aspect according to the invention, a plant is provided of the type mentioned in the opening paragraph, but which automatically orientates the components in the correct way during the production process.  
         [0015]     In a sixth aspect according to the invention, a plant is provided of the type mentioned in the opening paragraph, but which has a conveying system that is used in the separating and assembling operations.  
         [0016]     In a seventh aspect according to the invention, a method is provided of the type mentioned in the opening paragraph to, in a simple, cheap and effective way, assemble injection-molded plastic components of different kinds into finished products at a higher rate than known hitherto.  
         [0017]     The method according to the invention comprises injection molding of the components in such a way, that at least two components have a common sprue for each inject-molding operation and that the sprues are used for transporting and/or assembling the components. The sprues are conventionally disconnected from the components immediately after each injection-molding operation, whereby the components need to be orientated before at least the assembling operation. This orientation process is labor-intensive and costly. This problem, however, is advantageously remedied by according to the invention using the sprues for transporting and assembling the components manually or by means of robots.  
         [0018]     The plant according to the invention comprises a conveying system for conveying the sprues, still connected with the components, formed during the injection-molding process, from the injection-molding machines to the assembling station in such a way that the sprues arrive to this station in a predetermined orientated state.  
         [0019]     The mold for injection-molding a component is normally equipped with channels for injecting the hot and plasticized plastic into the cavity formed in the mold for molding the component as a cast of the cavity, thereby at the same time also molding the sprues as a cast of the channels. For obtaining a large production rate and an economic production, the mold will normally be designed to mold multiple components simultaneously, whereby these components get a common sprue.  
         [0020]     As is clear from the above-mentioned explanation, the sprues are necessary for injection-molding the components. But in a conventional plant they are labor-intensive and costly to handle in the subsequent production where they are normally separated from the components in a production step immediately after the molding operation.  
         [0021]     In contrast, the sprues, in the plant according to the invention, are utilized in the production process for carrying the components from the injection-molding machines to the assembling station in a predetermined orientated state, allowing the components to be securely, easily and quickly assembled, resulting in a high production rate with less effort and cost than in conventional processes.  
         [0022]     A feeding robot can be placed at each injection-molding machine for catching the sprues, when being ejected from the injection-molding machine, and carrying them at least part of the way to the assembling station. In addition at least one assembling robot can be placed at the assembling station for receiving and assembling the components. The orientation of the components, which arrive at the assembling station, is therefore advantageously predetermined already from the beginning of the process.  
         [0023]     The conveying system can, when only a smaller production capacity is required, be arranged in such a way that the assembling station receives the sprues, connected with the components, directly from the feeding robots. The plant according to this embodiment is very simple and cheap.  
         [0024]     When a larger production capacity is required, the conveying system can be comprised of at least one conveyer extending between the feeding robots and the, at least one, assembling robot. The feeding robots feed the conveyer during production with sprues, connected with the components, which at the end of the conveyer are handed over to the assembling robot. The conveyer can, in a preferred embodiment, comprise one or more rails, each having a longitudinal groove for accommodating at least one part of each of the sprues. The conveyer can moreover have means in the form of pneumatic cylinders or air jets for slidably displacing the suspension parts in the longitudinal grooves. The part of each of the sprues is in this case formed as a suspension part, which the feeding robots insert in the longitudinal groove, during the production.  
         [0025]     For ensuring that the sprues with the components arrive at the assembling station in the desired orientation the suspension parts and the grooves can be formed in such a way that the suspension parts cannot turn or only turn a little in the grooves around an axis extending in the longitudinal direction of the actual rail. The components will therefore always be kept in the same or nearly the same orientated position in planes extending perpendicular to the rails.  
         [0026]     In an advantageous embodiment, where the suspension parts are securely guided in this way in the grooves, the cross section of each groove of the rails can have the shape of a cross and the suspension part of the sprues has a corresponding cross shape.  
         [0027]     The component will also be kept in the same or nearly the same orientated position in planes extending in the longitudinal direction of the rails when each sprue has more than one suspension part, whereby the sprues are prevented from turning around axes extending perpendicular to the planes. When each sprue is formed with only two suspension parts interconnected with a cross bar it is advantageously obtained that the sprues are allowed to pass curves on the rails without bending the cross bar, which often consists of stiff plastic.  
         [0028]     The conveying system can, for obtaining a very large production capacity, have one or more main rails, each of which is connected with one or more branch rails each being fed by a feeding robot with sprues interconnected with components. The main rails are then supplied with the sprues from their associated branch rails, whereby the different components are conveyed to the assembling station by means of each of their main rails in positions orientated in such a way that the components quickly and easily can be assembled to the desired product. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     The invention will be explained in greater detail below where further advantageous properties and example embodiments are described with reference to the drawings, in which  
         [0030]      FIG. 1  is a flow chart for an embodiment of the plant according to the invention for producing products assembled of injection-molded plastic components,  
         [0031]      FIG. 2  shows in a larger scale, seen in perspective, a part of the conveying system of the plant with a number of rails,  
         [0032]      FIG. 3  shows a section taken along the line III-III in  FIG. 2 ,  
         [0033]      FIG. 4  shows a fragment of the same in a longitudinal section, seen from the side,  
         [0034]      FIG. 5  shows a section of another embodiment of a rail to the conveying system,  
         [0035]      FIG. 6  shows a fragment of the same in a longitudinal section, seen from above,  
         [0036]      FIG. 7  shows, seen in perspective, a fragment of the rail shown in  FIGS. 3 and 4  formed with an in-feed for the components,  
         [0037]      FIG. 8  shows an assembling station for assembling the component to a finished product,  
         [0038]      FIG. 9  shows a product produced by means of the plant, and  
         [0039]      FIG. 10  is a flow chart for another embodiment of the plant according to the invention for producing products assembled of injection-molded plastic components. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0040]     The plant shown in  FIG. 1  is in this case used for producing a product assembled of three different injection-molded components. The product and the components are shown here only as signatures.  
         [0041]     The plant comprises a first, a second and a third production line  1 ,  2  and  3 , an assembling station  4  and a conveying system  5  consisting of a first conveyer part  1   a  of the first production line  1 , a second conveyer part  2   a  of the second production line  2 , and a third conveyer part  3   a  of the third production line  3 .  
         [0042]     The first conveyer part  1   a  consists, in this case, of a first main rail  1   b , which is connected with two first branch rails  1   c ′ and  1   c ″, the second conveyer part  2   a  consists of a second main rail  2   b , which is connected with two second branch rails  2   c ′ and  2   c ″ and the third conveyer part  3   a  consists of a third main rail  3   b , which is connected with two third branch rails  3   c ′ and  3   c″.    
         [0043]     The first production line  1  comprises two first injection-molding machines  1   d ′ and  1   d ″ for injection-molding a first kind of injection-molded plastic component  1   e , the second production line  2  comprises two second injection-molding machines  2   d ′ and  2   d ″ for injection-molding a second kind of injection-molded plastic component  2   e , and the third production line  3  comprises two third injection-molding machines  3   d ′ and  3   d ″ for injection-molding a third kind of injection-molded plastic component  3   c.    
         [0044]     The first production line  1  further comprises two first feeding robots  1   f ′ and f″ for placing the sprues with components  1   e  injection-molded by the two first injection-molding machines  1   d ′ and  1   d ″ on the two first branch rails  1   c ′ and  1   c ″, the second production line  2  comprises two second feeding robots  2   f ′ and  2   f ″ for placing the sprues with the components  2   e  injection-molded by the two second injection-molding machines  2   d ′ and  2   d ″ on the two second branch rails  2   c ′ and  2   c ″, and the third production line  3  comprises two third feeding robots  3   f ′ and  3   f ″ for placing the sprues with the components  3   e  injection-molded by the two third injection-molding machines  3   d ′ and  3   d ″ on the two third branch rails  3   c ′ and  3   c″.    
         [0045]     Means (not shown in  FIG. 1 ) serve to push the sprues with the components in the direction of the arrows along the branch rails to the main rails and further along them in the direction of the arrows to a separating and assembling station  4 .  
         [0046]     The assembling station  4  comprises two assembling robots  4 ′ and  4 ″ for first assembling the first and second components  1   e  and  2   e  on the second main rail  2   b  and then assembling the already assembled components  1   e , 2   e  on the second main rail  2   b  with the third component  3   e  on the third main rail  3   b  to the finished product  1   e , 2   e , 3   e , which in the direction of the arrow is carried to a packing station and/or a storage (not shown).  
         [0047]      FIG. 2  shows in perspective and in a larger scale the first conveyer part  1   a  with the first main rail  1   b  connected with the two branch rails  1   c ′ and  1   c ″ by means of connections  1   g ′ and  1   g ″ guiding the sprues with the components  1   e  from the branch rails  1   c ′ and  1   c ″ into the main rail  1   b  along curves  1   h ′ and  1   h ″ merging with the main rail  1   a.    
         [0048]     The sprues with the components  1   e  are, during the production, pushed in the direction of the arrows along the branch rails  1   c ′, 1   c ″ to the main rail  1   a  via the curved connections by means of pneumatic cylinders  5  and along the main rail  1   a  towards the assembling station.  
         [0049]      FIGS. 3 and 4  show, in a first embodiment, e.g. the main rail  1   b  with injection-molded components  1   e , which are still connected to the sprue  6 , which is injection-molded together with the components.  
         [0050]     The sprue has two suspension parts  7  connected with a cross bar  8 . Each of the components  1   e  is connected with the cross bar  8  by means of a tenon  9 .  
         [0051]     Each suspension part is formed with a cross  10 , which is inserted into a correspondingly shaped longitudinal groove  11  in the rail  1   b . Each suspension part is furthermore formed with a spacing piece  12  for keeping the sprues with their components at a predetermined mutual distance from each other when being pushed along the rail. A rib  13 , which is formed on the rail, serves for hanging up the rail to e.g. the ceiling of the building in which the plant is situated.  
         [0052]     Due to the cross shape of the groove and the suspensions parts and also to the fact that the sprue has two suspension parts placed at a mutual distance from each other, the sprue and thereby the components are prevented from tilting in any direction in relation to the rail. The components will therefore advantageously arrive at the assembling station in an already orientated state, whereby it is possible to securely, quickly and easily assemble the components.  
         [0053]      FIGS. 5 and 6  shows e.g. the main rail  1   b  in a second embodiment. An air tube  14  is formed at the side of the rail. This air tube is connected with a supply of pressurized air (not shown). The suspension parts  7  of the sprue  6  with the components  1   e  is guided in the longitudinal groove  11  formed in the rail. In the wall  15  between the air tube and the groove a number of air nozzles  16  are formed for, in a direction forming an acute angle with the conveying direction shown by the arrow, sending air jets  17  against the components during operation of the plant, thereby blowing the suspension parts along the rail.  
         [0054]      FIG. 7  shows a fragment of e.g. the first branch rail  1   c ′. The first feeding robot  1   f ′ seizes, during production, the sprue  6  with the components  1   e  in synchronization with the production rate of the first injection-molding machine  1   d ′ and inserts the suspension parts  7  in the longitudinal grove of the rail. This operation is safely and accurately made by means of an in-feed  18  formed like a funnel.  
         [0055]      FIG. 8  shows the separation and assembling station  4  for the plant according to the invention. It is, by way of example, assumed that the product produced by means of the plant is a regulator  19  to the infusion set described in Swedish patent application SE 0300137-7. This regulator  19  is shown in  FIG. 9  and is assembled of three injection-molded components, namely a housing  20 , a floater  21  and a cap  22  with a spike  23 . The sprues with these components are pushed forward on the main rails  1   b , 2   b , 3   b , the floater  21  on the main rail  1   b , the housing  20  on the main rail  22  and the cap  23  on the main rail  3   b . The rails are in this case placed above each other but could also be placed side by side. The sprues and thereby the components are, as previously mentioned, correctly orientated when arriving at the assembling station thereby allowing the robots  4 ′ and  4 ″ to securely, easily and quickly assemble the components. The components are separated from their sprues by means of e.g. shears (not shown).  
         [0056]     The assembly operation takes place in the following way. The assembling robot  4 ′ seizes the floaters  21 , which are now separated from their sprues on the first main rail  1   b , and places them inside the housings  20 , while these are still connected with their sprues on the second main rail  2   b . The assembling robot  4 ″ then seizes the assembly  24  of the housings  20  and the floaters  21 , which are now separated from the sprues of the housings on the second main branch  2   b , and assembles this assembly  24  with the caps  23  on the third main rail  3   b . The assembled regulators  19 , which are still connected with the sprues of the caps on the third main rail  3   b , are on this main rail then transported to a packing station and/or a storage station (not shown), where the regulators are separated from the sprues and packed into packaging for being supplied to the consumers, e.g. hospitals.  
         [0057]     By means of this embodiment of the plant according to the invention a very high output can be obtained. As an example, the output of a plant for producing products composed of 3 parts, having three production lines each fed by 9 injection-molding machines is about 11.000 finished products per hour.  
         [0058]     In a variant of the above-described plant there is only one production line, which alternatingly is fed with components from two or more injection-molding machines. The assembling station then is arranged for assembling the components arriving to the assembling station in this way. This plant is suitable for productions where a very high output is not required.  
         [0059]      FIG. 10  shows another embodiment for a plant according to the invention for producing a product assembled of two different injection-molded components  25  and  26 . Also in this case there is only one production line, which fundamentally corresponds to the production line  1  shown in  FIG. 1 . The same reference numerals as in  FIG. 1-9  are used for the same parts.  
         [0060]     The six components  25  and  26 , are respectively, during the production, injection-molded by means of the injection-molding machines  1   d ′ and  1   d ″. The components are in  FIG. 10  seen immediately after they have been ejected from the machines and are still interconnected with their sprues  27 , which in this case are without suspension parts.  
         [0061]     The feeding robots  1   f ′ and  1   f ″ catch hold of the sprues  27  and hand them over to the assembling robot  4 ′, which assembles the two parts  25  and  26 .  
         [0062]     The two sprues  27  are, in this case, formed in such a way that the mutual distance between the six components  25  is the same as the mutual distance between the six components  26 . The components  25  and  26  can therefore be assembled while still being interconnected with their sprues  27 , thereby improving the speed of the process greatly and even further avoiding the troublesome process of having to orientate and assemble components that have already been separated from their sprues after the injection-molding process.  
         [0063]     A further robot  28  catches hold of the assembled components still interconnected with their sprues  27  and brings them to a separation and packing station (not shown).  
         [0064]     From the above, it is obvious that keeping the components on the sprue is not only advantageous when using a conveyor system comprising of rails, but also advantageous when the sprues are transported by other means between the different stations, such as an assembly station and a packaging station.  
         [0065]     As can be understood, it is essential to keep track of the orientation of the sprue, e.g. by robots or rails, whereby the sprues will be transported and assembled quickly and easily and at a much faster rate than if the components were separated from their sprue immediately after they were ejected from the injection-molding machine.  
         [0066]     In the above named description is with reference to the drawing described fully automatically operated embodiments according to the invention using the sprues for transporting and assembling the components.  
         [0067]     The sprue can, however, within the scope of the invention also advantageously be used for manually transporting and assembling the components.