Abstract:
The process is for producing in particular an internal conduit and is applied using a mould for realising a plurality of internal conduits for transport of a liquid which is entirely made of plastic material. The mould includes a top die which is translatable with respect to a bottom die and also includes two cores for realising internal profiles of the internal conduit, and an extraction plate associated to a plurality of extractors for expelling internal conduits from the mould at completion of the production process.

Description:
BACKGROUND of the INVENTION  
       [0001]     The production process relates to a moulding process of a liquid conduit internal of a water gun, comprising an interception device of the fluid.  
         [0002]     Water-cleaning guns are known in the prior art, and are connected to water-cleaning machines, and often include various forms of internal conduits for transport of a liquid, which conduits are shaped according to the performance type required of the guns, and the market sectors the guns are aimed at.  
         [0003]     The guns, which work at high pressure regimes, have to be able to support the pressures they work at, preventing any possibility of internal explosion and thus ensuring a reliable working life. They also obviously have to guarantee a good seal of the liquid running through them.  
         [0004]     To prevent the problems cited above, in the prior art the internal liquid transport conduit is generally made of an assembly of metallic conduits.  
         [0005]     More precisely, the assembly is composed of a first tract of conduit which is connected to the detergent liquid aspiration pipe, and internally contains a ball mechanism for opening and closing the liquid supply at the moment when the operator presses the gun trigger to activate the mechanism.  
         [0006]     A second tract of conduit is connected to the first tract, for expulsion of the pressurised liquid.  
         [0007]     The connection of the two tracts is realised preferably by a thread, which requires a rather laborious assembly stage.  
         [0008]     This production process, apart from having the disadvantage of incurring high production costs due to the choice of materials, also has the further drawback of slow manufacturing times of the single components and the complexity of the assembly stages which lengthen production times.  
         [0009]     Consequently, in order to reduce production costs, some gun models have been produced in which the transport conduit is made of a plastic material, which however leads to a compromise in relation to the technical functioning characteristics.  
         [0010]     The realisation of the whole assembly in plastic implicates the use of three components.  
         [0011]     In addition to the first and second tracts of conduit, an obturator mechanism is interpositioned, which has the function of the ball mechanism as described above.  
         [0012]     This mechanism has many functional limitations, among which seal problems due to the presence of many organs and the possibility of excessive play appearing between them.  
         [0013]     Furthermore, in this embodiment there is the drawback of an uncertain action mechanism of the gun, which is rendered difficult due to the presence of a return spring in opposition to the obturator mechanism, which contrasts the friction and at the same time generates an elastic behaviour which retards the actioning and arresting phases of the gun.  
         [0014]     Although production costs have been lowered by the choice of plastics for the materials, the appearance of an additional component, also in plastic, is not very significant in terms of final production costs, but does make assembly times longer.  
       SUMMARY of the INVENTION  
       [0015]     The main aim of the present invention is to provide a process for production of the internal liquid transport conduit, with which a good compromise between production costs, assembly costs and technical, functional and duration performance can be reached.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     These aims and advantages, and more besides, are all attained by the invention as it is characterised in the claims that follow.  
         [0017]     The invention is described herein below in detail, with reference to the accompanying figures of the drawings, which illustrated a preferred embodiment.  
         [0018]      FIG. 1  is a schematic view in section of an open mould for production of a water gun;  
         [0019]      FIG. 2  is a view in section of a closed mould for production of a water gun, in which a plastic material has been injected;  
         [0020]      FIG. 3  is a section view of an open mould for production of a water gun in which the moulded parts have been extracted;  
         [0021]      FIG. 4  is a detailed view of separation by breakage between the sprue and the moulded part;  
         [0022]      FIG. 5  is a schematic view in section of the injection chamber during insertion of the core elements;  
         [0023]      FIG. 6  is a detail showing the coupling between the two cores;  
         [0024]      FIG. 7  is a schematic view in section of the injection chamber of the material during extraction of the pair of cores. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     With reference to the above-cited figures,  1  denotes in its entirety a mould installed on a press of known type and not illustrated.  
         [0026]     The mould  1  exhibits a plurality of injection chambers  12 , preferably four, each of which is for moulding a liquid transport conduit  2  constituting the internal part of the water gun.  
         [0027]     The mould  1  is subdivided into a mobile part  4 , comprising a top die  5 , and a fixed part, comprising a bottom die  7  and a rest base  8 .  
         [0028]     The rest base  8  internally exhibits a cavity  9  for containing the bottom die  7 . The top die  5  and the bottom die  7  exhibit a plurality of coaxial through-holes  10 , preferably parallel.  
         [0029]     The plurality of holes  10  is coupled to a respective plurality of rods  11  in order to enable the top die  5  to translate with respect to the bottom die  7 , from a detached position to a position of contact.  
         [0030]     The top die  5  exhibits a lower surface  5   a  which, in the contact position, is near to an upper surface  7   a  of the bottom die  7 , in order to generate a common forming plane  21  of the moulded internal liquid transport conduits  2 .  
         [0031]     Internally of the plurality of rods  11  and at the position of the forming plane  21 , the top and bottom dies afford the injection chambers  12  for moulding the internal conduits  2  for transporting liquid.  
         [0032]     Each injection chamber  12  communicates with a common injection channel  13  which is a vehicle for pressure-injection of a molten plastic material.  
         [0033]     During solidification of the internal conduits  2 , a sprue  22  also solidifies within the injection channel  13 .  
         [0034]     The injection channel  13  exhibits a first tract  14  which crosses the top die  5 . The first tract  14  exhibits, on the top of the top die  5 , an inlet  14   a  which proceeds internally thereof with a plurality of branches  14   b , one for each injection chamber  12 , each terminating on the lower surface  5   a  of the top die  5  at the position of the forming plane  21 .  
         [0035]     The injection channel  13  proceeds with a plurality of second tracts  15  which from the upper surface  7   a  of the bottom die  7  proceed below the forming plane  21  up until they reach the injection chamber.  
         [0036]     The second tracts  15  each exhibit a first end  15   a  which connects to a respective branch  14   b , and a second end  15   b  which connects up to the injection chamber  12 .  
         [0037]     This conformation of the injection channel  13 , and especially the plurality of second tracts  15 , is made in this way in order to actuate a special injection technique known as submarine gate injection.  
         [0038]     Each second tract  15  develops below the forming plane  21  in order to allow, during extraction of the internal conduits  2 , an automatic breaking of the connection which forms between the sprue  22  and the moulded internal conduit  2 .  
         [0039]     In a second embodiment, not illustrated in the figures of the drawings, the injection channel  13  is constituted by a plurality of nozzles which inject a molten thermoplastic material directly into an injection chamber  12 .  
         [0040]     This conformation of the injection channel  13  is developed in order to obtain the process known as canal injection, preventing the formation of sprues and thus reducing to a minimum all waste materials.  
         [0041]     The internal liquid transport conduit  2 , which exhibits a first tract of conduit  3   a  connected to the aspiration tube and a second tract of conduit  3   b  for expelling the liquid, which first and second tracts of conduit are interconnected and arranged in an L shape, requires two cylindrical cores in order to form a single channel for passage of the fluid.  
         [0042]     For this reason, before the material injection stage, a pair of cores  16 ,  17 , are inserted into each injection chamber  12 ; the cores are respectively a long core  16  and a short core  17 , and are illustrated in  FIGS. 5 and 7 .  
         [0043]     The short core  17  is friction-housed at ends thereof  17   a ,  17   b , in respective chambers directed afforded in the injection chamber  12 , while the long core  16  has a first end  16   a  which is friction-housed in a chamber afforded in the injection chamber  12 , and a second end  16   b , opposite the first end  16   a , which has a plug-type end  18 , illustrated in  FIG. 6 , which couples with the cylindrical part of the short core  17 .  
         [0044]     The coupling enables, during the moulding process, obtaining of a single passage channel, avoiding formation, at the intersection between the first tract of conduit  3   a  and the second tract of conduit  3   b , of a film of plastic material which would have to be removed at the end of the moulding process.  
         [0045]     An extraction plate  19  is coupled to the plurality of rods  11 ; the plate  19  is interpositioned between the rest base  8  and the bottom die  7 , internally of the cavity  9 , and can be translated from a rest position in contact with the bottom of the cavity  9  of the rest base  8  to a work position, in contact with the bottom die  7 .  
         [0046]     A plurality of extractors  20  is connected to the extraction plate  19 , on the surface thereof which faces the bottom die  7 . Each of the plurality of extractors  20  terminates in the injection chamber  12  and is for extracting the internal conduits  2  from the mould.  
         [0047]     The plurality of extractors  20  comprises a central extractor  20   a  which terminates in the injection channel  13  and aids detachment of the sprue  22 , which solidifies internally of the channel, from the internal liquid transport conduit  2 .  
         [0048]     The production process for water guns functions as in the following description.  
         [0049]     The first stage, illustrated in  FIG. 5 , relates to the automatic positioning, using hydraulic pistons  23 ,  24 , of the cores  16 ,  17  internally of the injection chamber.  
         [0050]     The positioning is done while the mould is open, as in  FIG. 1 , i.e. when the top die  5  is in the detached position, held up by the plurality of rods  11 . First the short core  17  is positioned, then the long core  16 , so that the end  16   b  of the long core  16  can be coupled by the plug  18  to the short core  17 .  
         [0051]     Following the translation of the top die  5  along the plurality of rods  11  into the contact position with the bottom die  7 , the mould  1  is closed and the plastic material injected under pressure, see  FIG. 2 ; the plastic material can be a thermoplastic mix, for example polyamide including 30% of glass fibre.  
         [0052]     After the correct time lapse for solidification of the plastic material, the cores  16 ,  17  are extracted, as illustrated in  FIG. 7 .  
         [0053]     The extraction operation is the reverse of the positioning operation, i.e. the long core  16  has to be extracted before the short core  17 , so as correctly to disengage the plug  18  from the short core  17 .  
         [0054]     Following extraction of the cores  16 ,  17 , the mould is opened, bringing the top die  5  into the detached position.  
         [0055]     At this point the internal conduits  2  can be extracted from the injection chamber  12  by performing a translation of the extraction plate  19  and thereafter the plurality of extractors  20 , along the plurality of rods  11 , as illustrated in  FIG. 3 .  
         [0056]     The location of the second tract  15  of the injection channel  13 , means that during extraction the sprue, which has solidified internally of the injection channel  13 , detaches automatically from the internal liquid transport conduits  2 , which have just been formed, as shown in  FIG. 4 .  
         [0057]     The second tract  15 , below the forming plane  21  and internally of the bottom die  7 , is a barrier to the free rising of the sprue, which breaks due to the cutting force generated following the forces exerted by the extractors  20  and  20   a  and the reaction of the second tract  15 .  
         [0058]     An advantage of the invention is to provide a moulding process which produces an internal conduit  2  of liquid transport made in a single piece of plastic material, which at the same time reduces production costs and assembly times.  
         [0059]     A further advantage of the invention is to realise the internal liquid transport conduit in a plastic material which can internally contain a ball mechanism for opening and closing a liquid supply.